I agree with the previous comment. Technically for locale-specific sites like .co.uk Google would prefer youre hosted locally as it uses this as an additional ranking factor BUT compared to site speed and all the other ranking factors this one is small enough in significance to where you don't need to lose sleep over.
In this video(https://www.youtube.com/watch?v=hXt23AXlJJU), Matt Cutts talks about this topic and says it is a factor like I already stated but this video is fairly old. Now there are many more items which can have a greater impact on your rankings than server location.
Think about this, all things being equal except for server location, if Google needs to decide whether to rank one of two sites #1, it'll choose the one with servers located in the country where the searcher is searching from.