Local Merc dealer, Tony Purslow, sent a mailshot last week offering full air con service. Cost was £150
They sent me a voucher for a free aircon check:
- antibacterial decontamination
- performance test
- recharge coolant

Other vouchers in the pack include £20 off next service and 15% off accessories. Also (less useful IMO) free "winter check", free "peace of mind" check, and 10% off tyres.