Drivetrain rattle

If it all started after they replaced the belt you should return and complain ASAP . Let them hear the noise and give them a chance to repair or rectify any possible faulty work .

Garage say it is nothing to do with the work they have done and is coincidental (of course). The car was returned to me in a dirty state also with grease and dirt marks all over the steering wheel and door panels...they also forced entry thru the rear hatch after locking themselves out of the car. I would like to name the garage but it could be litigious?

If any of the many mechanics I had employed treated a car like the way your car was , they would have been out of a job that day . Disgraceful way to treat a customer . Did they only replace the timing belt ? Always better to use a timing belt kit which includes tensioner and water pump . You can get a rattle and scraping noise if the water pump bearing is failing , often causing a water leak in the cooling system and drop in header tank . With a garage like that , it would be your word against theirs and they would just deny liability . Word of mouth can often be the best way in exposing such a " garage "

MG of Derby....took my well above average condition 45 that was losing about a pint of water a week and they replaced the HG/cambelt and tensioner/water pump etc.....car was left on a public road overnight and when i collected it had body damage and was filthy. Central locking had mysteriously stopped working whilst in their "care" and then 3 months later (last week August 2020) suffered a cambelt failure on the M1 whilst travelling to a family 80th birthday.
They recovered the car next day and said that the new water pump had failed causing the breakdown....they said they re did all the HG work and replaced the water pump then asked me to travel 20 miles to collect as they had transporter issues. The car drove ok for about 10 miles and then the rattling started and it is doing around 15 miles to the gallon.
Rover owners beware...they don't want to know now and have accused me of finding additional faults that they are not responsible for.
We live and learn!

A lot more information now available that was not in original post .........................................