Don't know the first thing about it and couldn't see any of the bits described. Got a local plumber out and he found a blcoked pipe,from the expansion tank and release valve I think? Anyway it cost an hour labour and seems to be ok for now. Just got the sky to fix which bust this morning and the car that someone kindly drove into! They say bad things come in threes so I should be ok for the rest of the year, lol.
And I can't be bothered sorting my typing drrors caused by my phone and my sausage fingers!