UVgold unvented cyclinder leaking tundish - London based help required

[GrahamSE1]

Just discovered water is constantly dripping out of the tundish (noticed from the overflow pipe outside dripping…) I beleive it’s coming from the prv as I appear to have a drip under that too and water dripping in tundish is cold. I’ve also discovered after finding this forum that I probably should have had it serviced in the last 6 years since I moved in! No immediate problems but is anyone London (SE1 just outside congestion zone with parking available) based or could reccomend anyone to help?

Thanks in advance - Graham