To save myself money, how much of the work can I do myself? i.e. can I
lay the armoured cable, and just get a sparky in to do the sockets/plug
either end?

You can do all of it. Legally, the council could even contract you to sign
it off at the end, too! Indeed, I've heard of it being done. A loophole
means that the inspector need not be approved. However, this won't apply in
your case, as the case in question involved someone who knew what he was
doing and had all the equipment and could write the inspection certificate.

Basically, you can do all the work in its entirety and then ask the council
to sign it off.

Christian.