£143 certainly sounds a lot to me, but if that is not an issue and you are happy with your progress and instructor, then stick with it.
If the money does become an issue, then as has been pointed out, there are plenty of alternatives. I fly with The Pilot Centre**Link removed.** at Denham who charge £115 dual for C152 or £125 for C172/PA28 (if you block book in advance - an extra tenner an hour if you pay per lesson). The full list of costs is on the above website. They are a helpful friendly bunch.
From reading others' posts, the same is true of almost all the flying schools so it just becomes a question of personal taste and ease of access.
Personally, I copped out due to time, weather and money constraints and ended up finishing in the States.
BP