It can be useful to get the car checked over with a service, as they can spot potential problems which would have otherwise got missed if you just took it to Kwik-Fit for an
+filter change. It's this that you're really paying the money for rather than the cost of parts involved.
For example, during my last service they spotted that the ball-joint on the lower wishbone arm was loose and would soon need replacing. It was loose to a degree that I couldn't notice it during driving, however after inspecting it in the garage with the car in the air it was clear that it did need to be looked at. This is something that would of otherwise been overlooked.
Unless you really know your stuff and can confidently say that you can look at a car and determine the current state of the brakes, steering, transmission, suspension, engine, body structure, etc. and know when something needs to be replaced, I'd recommend booking it in for a service.
Having said that, £250 is quite pricey for a service..... I certainly would expect to pay any more than £200 (incl. VAT).