Thanks guys for the recent input, and good wishes

Re the debris issue - I believed I had dropped a washer through this very gap, basically the back plate of the top tensioner. I checked within the cam cover and round the bottom pulley but found nothing. I checked the timing initially at the cams, without locking the crank, and unaware at that time of the timing mark on the pulley for tdc. I did not remove or change the belt though. This was my initial thought, though I did doubt that a washer could make this racket.
The car has maybe driven a mile or two since this happened, but no long runs. A mates mate was going to have a look at it for me on Monday which means me taking it to work for collection, around 16 miles.
I don't know whether to drive it or not now? Perhaps I should borrow a locking kit and check the timing properly before driving it. There are some photos earlier where I simply turned the crank to bring the cam marks to the notches on the casing, but as said, no tdc. 'Ralf' the project car had a similar noise but I kinda ruled out the timing at that point

Running round in circles now, and had arranged for the compression test to be done as that remains outstanding.
Timing issue also needs to be resolved I suppose, so I'll try and organise a locking kit to do it properly. There were no problems before I changed the stat and gaskets
