@Beardy I must have missed your original post and have only just seen this thread now. I have a few thoughts, that may be helpful.
For a while I thought about getting a used hard top for my TJ, but in the end I decided not to for a number of reasons. First, I am not sure how many TJs sold in the UK came with hard tops, but mine certainly didn't. So in my case fitting a hard top would not just be a matter of buying a hard top and slapping it on, it would also require a fair bit of additional wiring and switches to be fitted. Not insurmountable, but another complexity. The hard top weighs a reasonable amount more than my soft top, when I started to take my TJ off road I decided I wanted to keep the weight down as far as possible. I still wanted to run a soft top in better weather and that meant the hard top would be off the TJ at least half the year. I have enough space to store it, but it would still be another thing clogging up the drive.
In the end I bought a replacement soft top and bought the best I could see, the Bestop Twill top. I only needed a new 'skin' as all the soft top frame was already there. I am sure a hard top would be quieter, but the new top is definitely better than the one on the TJ when I bought it. I have absolutely no issue with warmth, the heater is more than efficient enough to get the relatively small TJ interior very toasty with the soft top.
When I looked I found the same as you, hard tops were scarce and when I did see one it was very pricey. I would not necessarily discount getting one from the US if they are significantly cheaper there. While there is no avoiding the duty and VAT (about 24% in total), those costs now apply to bringing anything in from EU countries as well. If you find one and don't want to retain the soft top it may well be economic to drive across, dump the soft top and return with the hard top fitted. There are a number of Jeep events in continental Europe you could potentially combine with this to make it an even more worthwhile trip. If the US is by far the cheapest source you may want to consider container shipping. I currently have some parts coming this route at the moment, once they arrive I will report back on how successful the experiment was, but I have had very positive feedback about the service from another UK TJ owner. The cost of shipping may well make it an economic option. In the end I did not do it, but I was recently quoted £250 for shipping a crate axle to the UK which I thought was pretty reasonable.
I hope that helps and good luck with your search!