How to cat-proof your house for under £5.00

This is Tweak. Tweak is a house cat with a problem. He can't help but scratch demolish wooden door frames. Nearly every door frame in our house has cat claw marks in and they're really bad. We've tried everything and have now just accepted that he's a cat, it's their natural behaviour and making him stop is mean. We've bought numerous cat scratchers - hell, we even spent £60 on wood and made one ourselves only for it to become more of a watch tower for our other cat than the intended scratching post. I think he only used the post in the picture because he knew I was going to bad mouth him and he wanted to make it look like he uses it...
The scratching has got to a point where I've considered glossing our beautiful wooden door frames in an attempt to get him to stop scratching. Then I had an idea. I got 4 Tesco own brand doormats and some upholstery pins. Cut the mats into strips and tacked the strips to the door frames. He can scratch as much as he likes as the mats have rubber backing so should last quite a long time and he won;t get shouted at for doing what's natural for him. We've kept his claws short and so far the scratching has subsided. I think the tesco-doormat-tacking-mission was a success.
Yes, OK, this is only really suitable for people who don't mind their doors looking like they have bumpers but, I'd rather spend £5 and not have scratched door frames than have to spend hundreds getting all of the woodwork re-done. Job done!