I have never done a full motion sim trip so cannot compare but have a little look at these guys.
Virtual Flight Centre
Located not too far from Gatwick. To sum up;
Old 737-200 of Ryanair's completely stripped out and turned into an NG model.
Visuals are pretty good, using flight sim scenery rather than the somewhat 'basic' visuals you can find in some of the full motion stuff. However, the flight model is not the standard Flight Sim stuff so it's more realistic.
Fixed base but believe me I got 'the leans' on a climbing turn out of LGW as we entered cloud. Motion is not the most important thing.
You fly with a real pilot, my guy was a Monarch 757-300 FO and we enjoyed a 'Monarch minimums' approach into Innsbruck, a trip from East Midlands to LGW, a circuit at LGW via London (I work at LGW so nice to see it from the air once in a while) and a few Greek Island (short runway approaches and a stormy approach to Hong Kong's Kai Tak at night.
Perhaps have a go at BA while it's half price but give these guys a try when the price goes back up!