For anyone planning to put a door through to their integral garage, i can confirm how much mine has cost, as i really struggled to find a clear answer online.
Mine was £1,450:
£550 Plumbing
£150 Electrics
£750 knock through and put in door to fire regs
To put it in context i had about 5 pipes to re-route over where door will be, including putting in a pump to get waste water from my boiler over the door to the gravity waste pipe on other side.
The wall that is being knocked through is blockwork garage side and just plastered house side, also not load - bearing. First place i had intended to have it in hallway was double skin brickwork and would have added about £700 more in labour and type of lintel required.
Electric work was just moving couple wires but i added a double socket garage side.