Service not done

For 2 years I used servicing stop for my car , the car was picked up on time and I stupidly thought all was well , that is until this year when they could not pick up my car due it first M O T ,due to the garage they use ( easy garage of Hereford ) not having any drivers ? So I went to another garage only to be informed by their mechanic that my car has not been serviced for at least 20 months looking at the oil and oil filter ( which was rusty ! ) my service light was on after the first service and is still on to this day ,I contacted servicing stop by email and sent photos of the oil filter , air filter and spark plugs that had to be replaced , I informed them I wanted a full refund for both of the services that they had been paid for and were obviously NEVER carried out .
I have just received an email saying they will pay £26 which is the cost of the oil and oil filter ???????? I am disgusted I have contacted a solicitor to take them to court , they obviously don't do a good enough check on the garages they use , they are too eager to take my money for a service they don't do.
I would NEVER recommend that anyone uses this company , they will take no responsibility , they are allowing cars to go onto the roads without the proper checks being done and people are paying good money and thinking their cars are safe when in fact nothing is being done to the cars at all, this is DANGEROUS AND IMMORAL