Have experience of MFS myself doing IMC and wife doing PPL training.
Standard of instruction unquestionably good
Plus points - the experience of flying into and out of a major airport putting a PPL pilot way ahead of general club experience. R/T etc. skills very valuable. I would say that if you got your PPL here you would be a far more experienced and confident flier than with a conventional club. My personal thoughts is that if I were interested to go commercial this sort of start would put you ahead of the game. You will be flying a lot in a 'controlled' environment.
Negative points - mainly the cost, you will spend a great deal of time in holding patterns and travelling to and from 'circuit' airfields. Also there are restrictions on both time and weather conditions out of Manchester Int.
If I were to offer advice (God help me!) I would suggest ab initio training (maybe up to solo standard) at a place where you can go straight out and do circuit work at the airfield and then progress to PPL with MSF.
Suggest a visit to MSF - they are very friendly lot there!
Must add that I don't know Barton so my comments only relate to MSF.