I'd be wary of asking at any local musical equipment shop for a fair realistic valuation.

I've heard enough bragging from lads who worked in guitar shops
who unscrupulously offered naive uninformed old ladies peanuts
for valuable collectable guitars once belonging to deceased relatives.

One nasty little shit at a pokey guitar shop in Ilford
boasted he got an early 60s Fender Strat for 50 quid
off an elderly lady
who was delighted because she didn't think it would be worth
even that much cash in hand !!!

[yeah, ok, he may have been a knobhead Walter Mitty telling porkies
to big himself up..
but on the other hand....]