Hey mate, I’m sorry to hear what has happened to your car! It’s absolutely heartbreaking when it happens and then you hear people trying to charge your ridiculous prices to fix it.
A very similar thing happened to my R in 2018, VW at the time wanted 8k for a new engine which of course I wasn’t willing to pay. Another forum member found me a 2017 engine with under 10k miles for £2.5k which came with all the internals such as turbo and intake. The garage I bought it from fitted it for £500 so 3k all in was a decent price I believed!
My friend with an S3 also required a new engine and he sourced his via ebay and it has been spot on too!
I would recommend to do some research and see if you can find an R that’s been in a rear end smash with low miles and take it to a reputable garage to be fitted! Much better than any option VW have! Good luck and let me know how you get on and if you need any other advice!