There are engineers and clock repairers totally different approach to cleaning and lubrication.
My guess he did not use CLOCK oil, did not remove the mechanism and did not clean it thoroughly. READ ON.
Type in search engine how to oil a clock or go to www.ehow.co.uk search for oiling windup clocks you will see there is more to it than just wiping with a piece of rag at the bits you can get to.
£350 is a fair price to remove the mechanism, taking the mechanism apart and cleaning every part of the workings which I've no doubt will include hands,dial and pedulum, then re-assembling with a 48hr time adjustment check. Ask their procedure of works.
Bob, January 2011