Jump onto a mortgage calculator and put the interest rate up to 10% - then see if your budget can still handle it. Interest rates might be low now but the minute inflation slows they will start to rise again.

Fiona is right - the rule of thumb is no more than 30% after tax. It might seem manageable to pay more than that at first but you really need to stick under that long term or you can't factor in emergencies like being sick for a month or needing a new washing machine or things like that.

Good luck.