On the positive side, you have lots of holidays to look forward to, especially if you are already using more than the leave you have been given as I assume you have at least the minimum 20 days. If you don't have leave left, your choices seem to be to ask for a couple of hours off to be made up flexi style, or ask for a couple of hours unpaid leave. Most decent employers should be able to accommodate a couple of hours for something as important as house hunting, especially as it's something that is typically restricted to day business hours, as you've found out.