I've used the Sim at Virtual in Gatwick - the instructor was a current airline pilot and was excellent with good advice and good briefings. The sim is housed inside an old 737-200 cockpit - its like a hybrid homebuilt sim. It is quite tricky to get the feel for it. Practice flying by attitude and you will be fine in the RYR sim.
I would suggest 2hrs min if you can afford it as 1hr does not give you much practice and flies by! It is what it is... it's not a proper fixed base sim but that is reflected in the price.
Good luck
