I'm not normally into squashing people when they are down, but since you keep trying to justify your mistake, I'm going to do so.
Since the house was previously a three-bedroomed one, any previous requirement for ventilation was satisfied so replacing a previously-removed partition cannot make the situation any worse than when the house was built. So no Building Regs requirement. Bricking up of windows hasn't regularly happened since 'Window Tax' was abolished in 1851.
In spite of the fact the question-asker merely asked about replacing a partition, you seem to want to invent additional requirements such as electricity sockets. I suppose you could argue the house might also benefit from the addition of a wash-basin in there, in which case Building Regs for Hygiene (Part G if my memory serves me) would also have to be met. In any case, if the mythical requirement for more sockets could be met using spurs, Part P would not have to be met.