These guys are very good:
https://www.sptuning.co.uk/index.htmlbut they may be a bit far away for you?
They're done a few of may cars and generally do a before and after dyno run to prove the effectiveness of what they've done. Best one of mine as an Audi A6 2.7 V6 diesel that went from 177bhp to 230bhp.
One thing to remember is that it only puts more stress on components when you're using the difference between the before and after figures. When you're pootling around it isn't stressing anything any more than normal. I've never had any issues with any of my cars after they've been remapped anyway.