Negotiating Fair Compensation for Repair Delays

I informed the tenant I was going on holiday; his boiler broke down while I was away, so there was a delay in picking up his message. My usual plumber was unavailable, so I arranged for someone to visit, and the boiler was repaired -it was only low pressure. From the initial text, to repair was nine days. The tenant is now asking for compensation at 25% of a month's rent. Is this correct?

View Related Handbook Page