If it's not too late for my tuppence worth ...
Desktop - Dell are good machines/value, but repuation for support is poor these days. Alternative (our policy) is good local supplier who will charge a touch more -also builds to your spec - but jump in the van and come round and fix it if it goes wrong - assuming you can't do without your machine for a week or so.
Laptop - try AJP, we've used them for years - lots of bang per buck - reasonable support (particularly if you are London based)
www.ajp.co.uk
Brgds
Tim
(edited for cr*p typing - twice)