Those I can recommend highly having had instructors who have graduated from their tuition and subsequently work for me:
Chris Caine (as previously mentioned), Dorothy Pooley (Sky Leisure - Shoreham), On-Track Aviation (Wellesbourne-Montford). There may be others who are just as good, but anyone walking through my door looking for a FI job having been trained by the above can forget the formality of an interview and assessment flight!