Sensible - £100 per hour plus VAT and landing fee is a little steep, even for the south coast. You should be able to get it for that even at a commercial club at a large commercial airfield with a landing card. Obviously the two companies I work for both could offer around that price which is how I know, but the intention is not to advertise because there are many that are similar price or cheaper. Force the people who sell you services to compete!
Interestingly the dual rate at £160 is not too bad. I think that the club you used may also be underpaying the instructors, as most do
That is one consideration when people are concerned at the cost of flight training. Remember you are paying an instructor as little as £6.25 per hour, in one club I know of (£12.50 per flying hour, takes about 2 hours work to fly an hour), for a very seasonal job that required £40,000 worth of self-sponsored training! We are all, to a degree, volunteers. I have so far only been paid for flying a tiny fraction of what I have paid out.