Northumbria Helicopters based at Newcastle have done them several times. They've got both R22 and R44. Obviously there's the cost implication of the transit so it all depends where you're wanting to go from.
Just as an aside, if it's a straightforward sightseeing trip you're after then make sure your operator has an AOC. I might be wrong but
afaik Carlisle Flight Training are just a training organization.