New bonneville Noisy tappets following service?

I just had my 2003 Triumph Bonneville serviced after covering 12000 miles (at a Non Triumph Garage but very good). Started running rough after being very well behaved. Valve clearences were out, new shims ordered and fitted. But although full power and running great, tappets are very noisy.

Any ideas? Valve clearences were re-checked and spot on.

Thanks
Mark