It is important to emphasise that the 'old guy flying a Slingsby Venture on his own doing tuition' is in fact a highly regarded commercially qualified instructor and examiner for a variety of aircraft types, whose reputation is above reproach. He has been in business for decades and his company should not be confused with the 'other' club, which only started operating in mid 2011.
Well said. Any implication that this individual is anything but "highly regarded" should be followed by an immediate apology.
As for the original poster...I too suspect he is something to do with another Club at the same airfield that cannot match the pricing of doing a NPPL on a Motorglider
There are many Grob 109s in military service and also HM Armed Forces Gliding Clubs - they are incredibly cheap to operate (~£40-50 per hour solo) because they don't burn as much AVGAS as normal Group As.
LJ