When commuting in an area with a lot of hawthorn hedges in the 80's I would've given my eyeteeth for any of the puncture protection stuff around now.

FAO Brigid: Seeing as you like the tyres currently on the bike (and how the bike handles with them), if I were you, I'd start with puncture resistant belts inside the tyres for now, and see how you get on. If you change your mind in a few months, you'll have had time to save up for new tyres.