Hi, we've only had Oz since Sunday, and this morning I managed to catch him having a wee... and during the process he was meowing... now do you think this is something to worry about, or is it just because he meows all the time, and it's just his way....?

I would keep an eye on it. If you haven't had him to the vet yet, mention it during your visit. It could be a sign of pain.

taking him on friday, just for a check up...

Yeah take him to the vet just incase, he might have a little infection or something so it hurts.
If the vet gives him the all clear... is he still a baby? you mentioned you've not had him long. Some kittens meow for their mummy when they go to the toilet, almost like I'm done - come see me.

he's 3 yrs old.... not too sure what is diet has been like, but I guess it was mostly dry.... slowly trying to move him onto a wet diet.. it'll be a slow process due to him adjusting to his new environment...