I completed an OSCE for a pre-reg placement for Thames Valley and it was pretty easy. There was a short maths test, consisting of 4 relatively easy questions; and a drug chart which I had to check - pretty easy (on the front it stated that the patient had a penicillin allergy... And guess what... he'd been prescribed amoxicillin!)
I stressed a great deal beforehand, but it was only 30 mins long and it was pretty straightforward.
I managed to get the place (but I took a different hospital placement - In my preferred hospital).