You probably could flash like the UK firmware which is a common one on international version, but we don't know how well it work with your current carrier
Do you know which CSC codes for UK are "general", i.e. not connected with any particular mobile company there in the UK? I'm thinking the first 3 from this list, maybe also the last one (XEU), but it's just a guess...
United Kingdom (VIR)
United Kingdom (BTU)
United Kingdom (EE) (EVR)
United Kingdom (H3G) (H3G)
United Kingdom (O2) (O2U)
United Kingdom (Vodafone) (VOD)
United Kingdom / Ireland (XEU)