Hello and welcome to WHRForums Michael!
You can find quite a bit of feedback about 1and1 if you do a search over at
www.webhostingtalk.com. Choose the "search titles only option" to get to the interesting stuff fast. I don't know how many are "high profile", but they are/were customers nevertheless.
One think to note is that UK customers, must buy from 1and1.co.uk, and the prices there are higher compared to 1and1.com.
Another thing to know is that your site will be hosted in Germany, not in the UK. This is of no importance if you use a .co.uk domain, but if you use another domain, then the search engines won't know that your site is "in UK", and you can lose some search engine traffic.
I hope this helps. Good luck!