Cabair display their costs on this site here
http://www.cabair.com/html/fw_prices1.htm
They also state
Flying School Membership, Landing fees, Approach fees, Flight test and
Test fees (where applicable) are not included.
And they charge approx £18 per landing (ex VAT) at Elstree
and at my home airfield of Rochester, they charge £5
which personally I think is a bit of a rip-off, I did 6 landings at Rochester on my last lesson and all I paid for was the standard fee for the lesson. Had I done that with Cabair it would have cost me at least an extra £30
I have no personal experience with Cabair but I do believe their fees are a tad steep