Yes - they certainly did use to exist, flew with them about this time last year for 3 flights. Eventually went to OSFC instead as there was a better deal on hours.
Flew G-OZOO....the thing I remember about that aircraft was that it's transponder panel unit slid backwards out of the panel during a steep turn!
Out of interest, I did a quick Google & came up with this, although I'm not sure it will be of any use to you, it does have a reference number listed;
http://www.creditgate.com/search/sea...%20Non-Limited