If it's needed to re-wire the 2 port controlled throughthe HL and cylinder stats (basic S plan) then yes it really should be an UV qualifed bod doing it as it's playing with a safety system. If it's a Y plan with unvented then it would probably only be the feed to the 3 port that would need tied into from the Hive so maybe not in that case.
@NP62 - What type of system doo you have - S plan or Y plan? You will need a dual channel Hive as they are the only ones that would give you HW and CH control and it throughputs a 240V switched live (SL) internally. Your boiler will probably already be using a SL @ ST10, so shouldn't be an issue. Wiring wouldn't be much different that it is already, there may be a bridged 240v @ the programmer which wouldn't needed but wouldn't see much else having to change.