That one's pretty simple - in the UK ATC is not allowed to offer visual approaches to IFR traffic. The request has to come from the pilot.
That said, I'd be lying if I said I'd never done it.
BF, perhaps you'd like to tell us about an example of how you ignore a (CityExpress??) company SOP (or the ANO for that matter) to cut a few corners in the name of expedition?