When I saw this thread a few days ago,did not think silly question,saw few replys all ok,thought end of it but some how turned into a dig about fast track plumbers and people asking questions ,others think foolish,have seen long term trainee plumbers try soldering without flux,perfect pipework with black burn marks around each fitting,blobs of solder on floor,have seen fittings placed on painted pipework and tried to solder
All to often now as soon as someone asks a question,people dive in.and have a go,what happens is people stop asking and struggle on,I have seen experianced tradesmen do the strangest things all because they are afraid to bring into question their street cred by asking a question
For what it is worth finchy,I think your question was quite reasonable as did the members who spent their time answering it and am sure should you have other questions,you will find many helpful answers