They turn up in Fultons before being dispatched to auction, both of mine were in the region of £200.
On the same subject No.4's converted by Geoff Hart of Cheltenham are in my eyes the best No.4 TR conversions out there.

All of Geoff's rifles had Brindles triggers fitted.

Edited to add that "Rearlugs" gave me the heads up on the Hart No.4 the night before the auction, I got it complete with sights for £110.