I get an hour's flying for under £30. 80kts cruise, 60 litre tank...no need for GA IMHO!
Maybe so for Spamcans, but I get an hours flying for ~£25/hour, 130kts cruise, 17 litres/hour, 80 litre tank, 30Kg baggage capacity at full fuel with 2 adults in my "GA" Pioneer 300. Similar performance can be had from many other GA types too, eg MCR01 (Rod1 would complain if I called it a Banbi
).
Therefore, IMHO the performance/economy of modern microlights, whilst excellent, is not a reason in itself to decide against a full JAR PPL, as comparable/better performance can be had with modern GA types.
For the small(ish) difference in training costs, I would go for the JAR PPL unless you are absolutely sure you will never want to progress on to night/IMC/Multi/whatever. Having got the licence, you can then choose from a wider range of aircraft, and fairly easily fly microlights if you so wish.