More generally, as advice for anyone needing to dispose of such a collection, I would suggest contacting local (or other - if the collector has any particular interest or affiliation) railway (or steam) society, or preserved railway (or supporting society); or there are various specialist dealers (see adverts in Railway Magazine, and elsewhere).
If there are photographs or slides, they too can have a value, and so can be included in the offer of the collection.
Dealer will give something, but will only be interested in items of value. So they are unlikely to want video tapes...
If just seeking a 'good home', without necessarily recompense, then society or preservation outfit is perhaps a better option - good stuff they can sell, stuff of low value they can put on the '£1/10p table' - and if in the end no one wants it, they too have a rubbish bin. And if the one first approached can't help, they can hopefully point you in the right direction to somewhere else. And to find one, in the absence of other knowledge, it's always a case that Google is your friend.
The RCTS (
www.rcts.org.uk) is a national society (there are others), with local branches (including one meeting in Coventry), that may be able to help.