Wrote a long reply then the computer decides to tell me there are more posts to view and it seems everyone has already put you right. So I'll shut up and go back to my large slice of cheesecake.
Seems like everything is in hand, and top marks Dave for your willingness to accept advice and criticism. Plenty who come on here that dont.
I'm always willing to accept advice and learn.
That's why I was able to put a new vanity unit with tap and sink in my daughter's downstairs wc with a new waste pipe to an outside drain which involved cutting the cold water pipe to an existing outside tap, soldering a 'Tee' to a new position for a new outside tap and two elbows to take the cold water pipe around the corner thus providing a feed for the sink (incidentally freeing a 'stuck' gate valve in the process).
I was (until this whole kitchen sink issue hit the fan) tiling it (pics below).
I may be slow (I wouldn't make any money if I did it as a job) but it is done right - or at least to the best of my ability.
My Dad had a philosophy which was "Do your best. If you do your best, nobody can criticise you because it is the best that you can do." If it wasn't your best, his next question was "Why not?" There was no such thing in my Dad's book as "That's good enough!" or "That'll do!" I try to live by this (which sometimes causes me both extra work, pain and anguish) but that's another story.
Regarding the sink, my daughter is a single Mum with two small children and not a lot of spare cash. By doing this job for her she's been able to have it done at least five days earlier than she would have otherwise and around £120 cheaper. The guys (I won't call them plumbers) that took the old sink out charged her around £80 to do just that and rather than loosen the tight nuts on the isolating valves (see pic 1, post it #1 this thread) to disconnect the taps, they simply sawed through the pipes so that they were flush with the top of the nuts. I won't tell you what I called those clowns afterwards! The same firm wanted north of £150 to fit the sink (i.e re-plumb the hot and cold water and re-do the waste pipes) - and that didn't include the sink or taps.
and
(above pic was 2 weeks ago)
Any tradespeople that come here get a grilling - not in a bad way you understand - so that I might be able to undertake tasks myself (except gas work and boiler servicing I hasten to add).
Several years ago we had an Ideal Minimiser boiler and for the first few years it worked fine. Then it started to play up. We had a BG Service Contract (Homecare 400 I think it was called) and I got to know that boiler's insides somewhat intimately - so much so that if I had the parts I could probably have fixed it myself.
In the end BG were just throwing parts at it - it had new burners, thermocouples, gas valves, heat exchangers, pcbs - about the only thing that hadn't been replaced was the exterior casing.
Each time an engineer came - some came several times and I got to know their names - they were questioned about what they were doing and why. It possibly irritated some but I learned a lot.
Same with roofers, builders, plumbers and plasterers - although I still can't get plaster to stay on the damned wall, no matter what I try.
I'll make the changes suggested so that only the trap (C) remains "wet".
Regards
Dave