I looking for a premium UK unmanaged VPS XEN ideally with following specs.
3-4 gb memory
200-300 gb disk
Open minded on budget for good service and specs.
Or would I be better with a value dedicated server.
The UK is primarily more costly because of the disgusting ever increasing power costs the energy companies are dishing out if you can bare with the additional pittance in latency you might want to look at France/Germany.
Personally, I wouldn't go for a dedicated even though those specs are on the borderline between a VPS and dedicated. A VPS will still offer, in most cases, better performance and reliability than a low end server. What about other things like a control panel? And what do you plan running on it, as that could change what you need.