Should I arrange any repairs myself?
Unless the equipment is something that you own it is up to PHA to repair faulty gas appliances. If in doubt always ask PHA to deal with the problem first.
If you ask your own engineer to check or repair an appliance, it will be up to you to pay the bill. If you are having an appliance that you own repaired always ask how much it will cost before you go ahead, and always use a GAS SAFE registered engineer. Never attempt to undertake the repairs yourself.