I to live in Watford and trained at Cabair from Elstree. I have no complaints about them. The only issue I had was having four instructors during my training, as they all were only there only to hour build on their KLM sponsorships.
I now run my plane from there and apart from the grumpy ATC there are some very helpful and freindly pilots.
Try a trial lesson with both firms and see what you think.