Looking at the list:
Obvious
services that lend themselves well to being sold online: webhostingprovider.co.uk (web hosting), freemobileapp.co.uk (app sales/development), accommodation.co.uk (accommodation), stocktrading.co.uk (finance), mmogames.co.uk (mass multiplayer gaming), dentalveneers.co.uk (dental veneers).
Products that lend themselves well to being sold online: esmokes.co.uk (electronic cigarettes),
grafitti.co.uk - trendy/cool/underground/artistic which would probably sell to some kind of online service provider.
"LLL" containing three good letters (and may have obvious uses, I haven't checked): tgi.co.uk, ipg.co.uk
Rejected that we know of:
queen.co.uk - no obvious commercial use comes to my mind. Not cool like graffiti.
vdo.co.uk - the "v" might spoil it (I've not Googled for anything else).
advice.co.uk - possibly too generic and no immediately obvious commercial use.
madrid.co.uk - Capital city of Spain. Why should this be particularly desirable within .uk? If it was spain.co.uk then much better, particularly with Spain being a very popular British tourist destination. I checked Barcelona.co.uk and it's parked.
elements.co.uk - plural so might reduce its appeal. No obvious commercial use springs to my mind.
All of this is
in my opinion which anyone is obviously free to agree/disagree with and of course to debate.