If you are not willing to relocate to cash out your crypto then everything you do would be useless.
When buying property the solicitors on both sides will require to see bank statements and an explanation on how funds were accumulated and if tax was applicable. When in a non tax country you are not liable and therefore you︀ can demonstrate you acquired it there and had enough and came back.
Lastly the amount︁ of stamp duty you pay is registered on your NI number. So if you have︂ only paid 4K tax but bought a 400K property you will be getting a demand︃ letter through the door.