Thanks, I'm going simply let him know what a trade would likely charge and let him come up with a price he'd like to pay, money really isn't an issue for him but simply finding someone he can trust to do the work reliably was his priority.
I had a minimum £500 trade quote in my head as a wild guess before £600 was mentioned, wouldn't expect a trade to do this for less and I'm guessing quotes could be considerably higher but as mentioned I have no experience here.
Can check back in when we've agreed a price in case anyone is curious.