Help! Tenants need temporary hot water while boiler repaired - any ideas?

[Smittals]

Any ideas please - am googling for water heater hire but so far just seem to be for industrial projects. Luckily the heating is working fine, but the poor tenants will not have had hot water for a week by the time I can get it fixed (thank goodness they don't have children!). If you have any bright ideas I'd be really grateful thanks.

Does the hot water tank have an immersion heater fitted in it? That is what we used to heat water while our boiler was fixed. Not much help if they have a combi boiler though!

If hot water tank but no immersion heater can you get one fitted quicker than getting boiler replaced. Always handy as a back up. Might be cheaper than trying to hire something. Other alternative is pay for few nights in a travel lodge or similar until it is fixed?

One of these?