1-flue needs to be sealed where it passes through the wall if a cavity wall sealed on both inside and outside.plaster for inside.sand and cement for outside.
if no attempt has been made to seal these gaps poc can creap into the bathroom,also making good the gaps also holds the flue in position...
take a sample of water from heat exchanger.if it looks very black its sludge.
if not too discoloured call back BG to investgate fault.show sample of water to them.
ask for a service enginner not a salesman
worcester ri series have not let me down yet.
ensure old system is correctly powerflushed and pay a litle bit more and have a magnaclean fitted. www.adeysolutions.co.uk
firstly try to isolate water elsewhere is ther a stopcock in pavement etc.then repair existing stopcock.
secondly a lead to copper stop cock is generally not available.you need a fitting called a lead lock,short piece of 15mm tube and then fit stopcock.
lead lock info/sizes see faq.s...
easy,have a drive around your local area,find national grid guys working,have a chat with them aand ask them if they are interested in a private job,if they dont want to do it they will know someone who is interested.
did you give the landlord a quote to bring the installation up to regs.
did you do a tightness test.check working pressure at hob.
or do you just do paperwork.
had same problem in a flat i had in hastings.
ie pipework under sized.
all i did was to run 28mm from boiler to 28mm pump valve (high head pump)and fit 28mm mid position valve.
gate valve on coil return and 28mm heating return boiler to first tee.
worked a treat.