Back top the OP's original comments and questions.
Bringing a water supply pipe into the building is not part of BRegs in itself, but you would have to comply with certain installation criteria set down by the local water company. This includes such things as minimum trench depth, pipe type etc.
Now the act of bringing that pipe into the building may result in you needing to comply with the Party Wall etc Act, depending on proximity to neighbouring foundations. This too has nothing to do with BRegs.
If you need to come in under the existing footing, technically that is structural work and requires BRegs approval.
You will need BRegs approval for hooking up to any drains and the install of bogs and sinks.
Thus, as the Feisty One
says, you can do the arranging for the pipework in and hooked up yourself, but, being a complete novice, it's probably best that you don't.
You don't need an architect, structural engineer or building surveyor, although any of these would be pleased to take your money off you and provide you with acres of shiney specifications, drawings and risk assessments to pad out their fee.
You don't need an architect's tech, who is a lesser-qualified version of the foregoing and ergo by rights should be cheaper.
All you need is a
sensible general builder, who has some idea of what he's doing, can liaise with the water company re the hook-up, who can submit a building notice for you if any part of the works demands it and who has a plumber mate who can sub-contract for the more complicated plumbing bits, if he's not up to it himself.
The only bit that leaves out is someone re the PWeA and with that it's best to try and avoid any need to invoke that particularly senseless piece of legislation if at all possible, otherwise that will only be someone else's pocket getting lined for this frankly two-bit job.
Thus, you need someone like Noseall - and the Woodster himself does this kind of thing too, despite him being qualified in a non-dirty-hand side of the profession.