@Xein I think you are just going to have to accept to either:
1: Order new direct from Renault you will get early 2022 (if you use Renault Finance they have the best deals if your credit is strong). With a £8.3K deposit they give you 0% APR over 48 months! otherwise 5.9-6.9% + up to £2.5K deposit is the best you will get.
2: Keep looking literally every single day at decent used but prices are rising fast not going to be easy to get the exact one you want anytime soon as some jokers are buying just to immediately slap a few £K more on the asking price!
Supply & demand is not likely to change short term. Renault are only selling across the whole of the UK 15-20 new RS 300 Series per month so production lines when they do run & they have all the parts its only every so often they even make them. I hear that Renault are also going slow on these next quarter as it means they come under the EU mandatory emission rules so less cars overall get produced last 3 months of every year to avoid heavy fines if they exceed the target quota for the year!
The real world price guide
should be something like (unless extreme miles):
RS280 2019 = £20-26K
RS300 2020 = £26-28K
RS300 2021 = £28-32K (lot of decent improvements on 2021 Phase 2 cars)
Should not really be much difference between used Sport & Trophy prices either as different cars for different uses. Sport is all round for some with a family (like most hatchback owners!) Trophy has less comfort so perhaps £500 difference between the 2 unless it has the ultra light Fuji alloys or sunroof which would add perhaps £2K for both used (new would cost you £2.3K extra). On UK roads I doubt a decent driver in a sport vs trophy challenge would notice any difference between the 2 from a-b on our roads!!
unless you are going on the track you sure Trophy Spec is something you actually need as it also comes with the Lithium battery issue which is still not fixed so the car needs the renault solution applied (main dealers do this not so sure anyone else does!).
950 miles Orange 2021 @ £36500 personally the price is too high for me but main renault dealer it will be gone within a day or so do not hang around!
2021 Orange Renault Megane 1.8T R.S.300 Trophy EDC (s/s) 5dr for sale for £36500 in Poole, Dorset (autotrader.co.uk)
7800 miles White 2020 @ £32999 main renault dealer again
2020 White Renault Megane 1.8T R.S.300 Trophy EDC (s/s) 5dr for sale for £32999 in Solihull, West Midlands (autotrader.co.uk)
Does not say miles Flame Red 2021 brand new £37995 (will be a cancellation) not a main dealer though!
Red Renault Megane 1.8T R.S.300 Trophy EDC (s/s) 5dr for sale for £37995 in Barnsley, Yorkshire (autotrader.co.uk)
Dealers are generally underhand as you well know no way does a non main dealer get the brand new 2021 Flame Red without some form of questionable business tactics when main dealers cannot even get them & would sell quite a few more if they could!
I purchased this the day I got it. In my opinion, if you have stone chips, you drive it like you should, not kept in a garage driven once, maybe twice a year.
its going to be a job you DIY. Get a little filler mask around so you only fill the area you need to. Gently rub the filler (ONLY!) down when dry. You need to order the Renault touch up kit (it contains primer, lacquer & liquid yellow J37 I think is the paint code but double checking before ordering this). Renault no longer sell the liquid yellow kit BTW. Best you can hope for is disguise the damage no way to get 100% but you can mask it pretty good.
Only selling a handful a month in all of the UK brand new so the production lines are not run as frequently as they used to be 
