A problem with tapping

Hello all, I apologise firstly if this is the wrong place to post, it's my first post but hoping for some answers in relation to to my mk4 mondeo titanium 2008 1.8tdci.

I've not had the car very long and decided to have the cambelt and wetbelt replaced by a garage I've trusted and used for mots for years. Usually anything serious or time allowing I carry out most work myself but a cambelt and wetbelt on these are quite tricky and I have no time these days to do such a task so I thought I'd go £600 in and let the garage sort it for once. So the garage done the job, on the day of picking up the car I received a phone call to say there had been a problem with the new tensioner,  they assured my it hadn't been out on a test drive and I do trust this guy, he said he heard after a few minutes some spooling, weird noise from the belts so he turned it off and noticed that the tension spring or tensioner had come loose. Assured me he caught it in time and it had jumped no teeth in the process. A new tensioner was ordered, during this time he took everything back out, rechecked all timing and refitted and all back together working. The problem I have is, when it starts from cold this engine sounds beautiful just as it did before it went to the garage but when it gets to normal operating temperature there is a loud tapping noise it seems coming from the top of the engine? (Tappets maybe?)

To add, there has never been smoke or anything from the exhaust and even now its completely free of any smoke cold or hot. I just know it never sounded like this before and I'm baffled and so is he. The tapping noise is prominent when you rev it to 2000/3000 rpm ,drive though a street etc, cars/walls either side of you reflecting the noise, people turn around to see what's clacking away behind them!

The parts replaced were, a new wetbelt and camblet kit, all tensioner and pullys replaced and a new oil pump in the process just to be safe. The car is on 110000 miles and is a lovely engine for its age.still pulls hard and no change in the drive of the engine. I'm just baffled as to what the noise could be or why it's doing it when hot?  He assured me he's put the correct 5 30 oil in, there is a chance the past owner could have been running it on 5 40 oil to negate the tapping noise but now I'll never know. Would 5 40 kill this engine if I tried it to see if noise dissappears?

Anyway, sorry for the very long post and hope I'm in the right place and hope I hear from someone soon who's experienced this. Many thanks in advance