Most of the UK companies have their servers in US or EU. When people ask for a UK host, i heard often mkhosting as the answer but i really don't know their services. Otherwise try to ping a few UK host and take the one with the fastest ping answer time.
Good luck by choosing your host and welcome on WHT.
You find many hosting companies in UK having datacenters in UK. Intially yes the hosting companies had datacenters in US, due to the feasibility and security they provide and their datacenters are robust datacenters . One of the famous and most reliant hosting company is Dataflame (dataflame.co.uk)