The actual parts wont cost that much to be honest. Where it gets expensive is the labour garage costs

Most garages will charge a minimum of £50 an hour labour. My car is booked into the garage next week to get some welding done as well. Been quoted £140 to weld up two rusted drainage holes under the rear floor pan. Most of that cost will be taking the carpets up etc and the prep work.
Im going to do most of the prep work myself to get the cost down.
It will be the welding work that will cost you the most. Which parts need welding?