Well, that depends on the hosting provider you choose.
If you have hosted your website on servers based in the UK, your website has a UK IP address.
Now, if you choose another hosting provider who offers servers based in the UK, the IP address of your website will be a UK based IP address only and hence it won't affect your website rankings severely

However, if you choose a hosting provider who offers servers based in the US, your website will be hosted on a US IP address which can definitely affect your website rankings in search engines
Hope this helps...