UK businesses may have an unduly negative attitude
No.. we are just less gullible that our US cousins!
As an IT Manager in the Financial services sector, I'd add the issue is much more diverse than security. There are other issues such as support, accountability and cost.
I'm currently managing an Infrastructure refresh project, our original design involved substantial use of cloud, but after running a 2 month evaluation (with Grid, IBM and EC2), the results were
1) It was more cost effective to buy our own tin
2) Getting support when a problem occurred was near impossible.
3) Account managers were only interested in getting the paper signed.. after which we couldn't see them for dust
Thats not to say Cloud is useless, its great for start-ups who don't have the cash to invest in infrastructure, who's scalability needs are unknown etc.
But our conclusion was, if you want something cost effective and know exactly what you need, want it to be reliable and well supported - do it yourself!