At Southend, I would recommend Flightcentre or Seawing: they share a lot of instructors and both have a low instructor turnover. Personally, I would say FC's acft are better turned out and a little cheaper. Seawing is a member owned club; FC is a business with a fairly clubby atmosphere.
I don't have any direct experience of SFC or Willow Air, but neither floated my boat when looking for somewhere to learn - both Seawing and FlightCentre struck me as the more friendly and inviting places and were the only ones that gave me a chance to speak to an instructor before booking.
Obviously this is based on my own personal opinion and experiences and won't be true for all!
