You mentioned you had 3 addresses, here's a 4th:
Dell Computer Corporation
Dell Campus
Bracknell, Berkshire
United Kingdom RG12 1FA
44-1344-860-456
Fax: 44-1344-373-138
My reason for posting this is really the phone no. I'm sure you have a few of those already but I think you really need the number for the main switchboard and not one of those queuing systems.
It's not clear to me from your message what your actual problem is but perhaps you should aim straight for their Customer Relations Dept. or (2nd best) Customer Services.
One other thing you can do is ring the switchboard and ask for the name of the most senior person in the UK (e.g. Country Manager, UK VP, MD or whatever terminology Dell use) and then ask to speak with that person. Ok, you'll only get their PA or the PA's secretary but if you are lucky you can rest assured everyone around that
senior person will likely want to put the matter to rest ASAP
I just
read that Dell UK is also their EMEA HQ so there will be some pretty senior people there!