Thanks for all the advice. As I am totally non-technical some of it is
a bit beyond me! However, there are a few things I should perhaps
clarify.

I have a warm air heating system which was there when I moved in
(almost new) which I am keeping so no chance of a combi. I have to
have the cylinder changed to an indirect y-plan system so I can have
rads running off, heated by the warm air unit water heater. This is
ok, it's just that I have been told that a megaflow is the only way to
get the hot taps running ok. I already have a nice new electric shower
installed. Basically it's just 3 sinks which are suffering and so
spending any more than is absolutely needed is going to be painfull! I
had a quote today of about £800 (just supply) which is nowhere near
what I was expecting!!

I spoke to a guy today who thought it could be the pipework which has
been used to install the new sinks - the bath is ok (fills faster than
any I have ever had before) and this is the original bath using the
original pipework. He said hot water pipes should be 22mm, but the
ones going up underneath the new sinks in my flat are 15mm. He also
said flexi hoses severely reduce flow, which have been used on 2 of
the sinks as far as I can see.

My guy said the bath has a better flow because it is lower down. It's
only a matter of inches - can this be true? Is it possible he has used
incorrect pipework and just doesn't want to admit it? When I asked him
he did not know that some taps were unsuitable for gravity fed systems
so the kitchen one may be useless anyway and the flow is pitiful. My
mains cold water pressure is very good indeed.

Another thing is he has installed a shower for me and the outside
drain became blocked and sewage came back into the shower! He admitted
he hadn't installed a non-return valve as they can get blocked
themselves so it's not a good idea. The drain unblocker guy said I
should have had one.

Am I being taken for a ride? This is why it's great to have your
advice as I would be none the wiser otherwise!!!!