Conversion of EASA ATPL to UK questions

[OrangeSkies]

I'm not entirely sure whether this is the correct place to post this and if not here, mods please direct to the best subforum.

I was issued a UK ATPL many moons ago and have been working for a UK carrier since. Unfortunately, I temporarily lost my medical nearly 2 years ago. I am now heading in the right direction to getting it reinstated. That's the good news, the bad news is it seems like a minefield of legal speak trying to understand exactly where I stand, come the end of the year, with the full transition to UK licencing.

I am not too sure where I stand. My licence is a blue UK CAA Flight Crew Licence. Within in it, my licence number starts GBR.FCL.AT.xxxx. This on the face of it would lead me to presume that it is an already converted licence. I know that I have registered with Cellma in the past and have had a UK CAA Class 1 medical certificate pertaining to a Part-FCL Licence issued in accordance with Part-Med in Jan 2021. However, I don't for the life of me recall actually completing any forms for the UK CAA for a licence conversion. I'm not sure if my employer did this for me?

My first question is, how would I know whether my UK->EASA->UK licence has already occurred or whether I remain UK->EASA still?
My next question relates to somewhere on the CAA site, it mentioned that an EASA licence holder can not apply for a UK licence unless they hold a valid medical. Would the circumstances that I previously held a UK licence and only changed to EASA due to the mandatory licencing mean that the UK CAA would allow me to convert this back even after the 31st Dec 2022? Likewise, is it simply a case of completing the paperwork before the 31st Dec 2022 or does it have to have been signed off by the CAA before that? The CAAs site suggests that there can be a large backlog and I'd have thought with any deadline, there will always be a deluge of applications before the cutoff. Hence, I'd hate to submit my conversion paperwork to the CAA before the closure and think that all is well, only to find that the CAA don't process it in time due to backlogs and I miss the cutoff.
My final question is a worst case, should it be that my licence is not a UK one and I can not get my medical or licence granted in time. What are the ramifications? I read somewhere something like the ATPLs would need to be retaken, is this correct? Would any flight testing be required? This would seem very harsh for a UK pilot with total jet commercial flying hours in the 5 digits, who had been flying up until sickness 2 years ago.

Very interested in both thoughts and views. May I kindly request that if it is merely your thoughts on the subject, please included text to this effect. Likewise, if you are a licencing guru and are completely adept at SRG documents and forms please also include this. I'd prefer not to pull any more hairs out with conflicting information or hearsay.

Many thanks for your time.