First of all, welcome to the forum!
As for your specific questions:
Other schools will be giving you the hard sell because a) winter is a lean period for flying organisations b) students are thin on the ground and they would like to lock you in and c) they need the cash!
My advice would be never pay more up front more than you can comfortably afford to lose. - Eg two schools (one very large, one small) have gone bust at Cranfield in the last 6 months, it is highly improbable that anyone will get their money back.
As for the NPPL vs PPL, go for the PPL - you will inevitably have the requisite hours by the time you finish and it offers more flexibility later on.
Having a PPL TMG rating and an SEP rating (Cessnas etc) will be useful after you qualify as you can count the hours in both types of aircraft towards your experience - again a more flexible option.
As for Hinton, Clive Stainer is the CFI and has a good reputation as well as years of experience. There has been significant investment in the club recently, with an expanded fleet and improved facilities. I visited recently and was told that they had a policy of using more experieinced instructors rather than recently qualified staff, which is good news for the student.
The other aspect of course is that a lower training cost leaves you more cash to use for flying once you qualify!