* It's good that you brought this issue up. My feet are not as extreme as yours, but I do have flat feet due to fallen arches. So I'll share some tips that I hope will save you some (further) grief.
* If your podiatrist determines that you need prescription orthotics, make sure the podiatrist has experience prescribing orthotics for figure skates. I'm in the US, not many here do. Orthotics need to be designed to correct foot anomalies for specific activities. I have one pair for walking shoes; another for running shoes. Figure skating is radically different since (a) the foot doesn't flex much along the arches (which it does in walking and running), (b) figure skating is strongly controlled by biases towards inside/outside edges (not a factor in walking and running), and (c) advanced figure skating boots typically have well-defined heel cups (heel cups integrated with orthotics can interfere with the heel cups in the boots). Since I couldn't find a podiatrist experienced with figure skating boots, I ended up making my own corrective insoles (with some help, but that's a story in itself).
* Make sure your fitter is aware of your issues and ask them to take measurements and tracings under multiple conditions. E.g., sometimes measurements and tracings are done only while the skater is sitting (non-weight-bearing). Sometimes, a second set is taken when the skater is standing straight (weight-bearing). And, sometimes, a third set is taken when the skater is standing with bent knees (weight-bearing with flex).
Be extra careful if you are being measured with the Jackson scanner. It uses a glass platform tilted ~45 deg from the plane of the floor. Measurements are taken only with the skater in the sitting position. Prior to the introduction of the scanner, manual measurements and tracings were taken both with the skater sitting and standing straight. In my case, the scanner gave erroneous results (I believe because it didn't take into account foot width differences in non-weight-bearing and weight-bearing positions). It spit out an 8R size; whereas I had been wearing an 8W size (as determined from prior manual measurements and tracings). After a discussion with my fitter, I decided to stick with the 8W (since I'm a male skater, boots typically need to be special ordered, so it wasn't simply an issue of trying on both). With heat molding and supplemental punching to square off the toebox some (I have Orient-shaped feet), the fit was fine (with snug heel pockets). The 8R would have been too narrow.
* Whether you are fitted with prescription orthotics or OTC corrective insoles, your boots will need to have room to accommodate them. This becomes somewhat a tricky chicken-or-egg scenario. Ideally you would like to be fitted for orthotics and boots at the same time. As far as I know, only Harlicks (US) does that for their customs. But given their long delays and your location in the UK, that's not likely a viable option. So you typically need to purchase the boots first and then get orthotics/corrective insoles afterwards.
When looking for a boot, look for what boot manufacturers call high volume (referring to internal vertical height); particularly in the toebox, but along the instep as well. I have the Jackson Supreme 5362 (men's counterpart of the women's Supreme 5300). It does have high volume, along with the added advantage of what they call their wide cuff design. There was a previous thread in which many skaters complained that the tongue would slip sideways and one side would be exposed (not covered by the throat of the uppers). This appeared to be the norm for many models of boots from different manufacturers. Jackson has solved this problem (at least for some of their models) by designing the tongue and uppers such that on each side the throat of the uppers and the side of the tongue overlaps by nearly one inch.
This is important, because addition of an orthotic or corrective insole will cause your foot to sit higher inside the boot, pushing out against the tongue more. The wider cuff allows more accommodation (less likely that one or both sides of the tongue will be exposed) simply by adjusting the lacing. When you are checking out other models of Jacksons or boots from other manufacturers, look for this feature. It will save you a lot of grief. [I have an older model of Jackson that does not have this feature; it does make a substantial difference.]
ETA: When you get your boots heat molded, wear your orthotics/corrective insoles instead of the manufacturer's stock insoles. Orthotics/corrective insoles generally cannot be baked with the boots, but they can be inserted into the boots after the boots are baked, and before you insert your feet. Depending on how you schedule things, you may need an initial heat molding with the stock insoles, do some initial break-in, get orthotics/corrective insoles, and then do a follow-up heat molding with the orthotics/corrective insoles.
* Sorry for the long post. You have a lot to wade through.But you have a lot (foot health and money) at stake.
Don’t apologise at all. I really appreciate you taking the time to give me this information. I will definitely take all of this in consideration now. Wow there is so much to learn and know but I hope all of this will finally lead me to a solution and allow me to skate comfortably.
Also thank you for warning me about the Jackson scanner. That would have been an issue for me because if I measured correctly there was atleast 1cm difference between when I sit and stand. There’s definitely something going on with my feet especially the arches. Aside from the orthotics do you feel that any exercises have been beneficial for the fallen arches?
The high volume makes a lot of sense. I was even told that I couldn’t get custom insoles in my current debuts because there isn’t enough space. I am already struggling with volume without any insole to be honest.
I keep hearing great things about Harlicks, really wish it was possible over here.
Thanks again I will make sure to consider all these factors going forward!
But you have a lot (foot health and money) at stake.

