I too fly in a SEP group as well as owning my own microlight.
Ownership does have the huge advantage of allowing you to use the aircraft whenever you like, and go away for as long as you like, so a £4k microlight would certainly let you take to the air whenever you felt like it, rather than having to work around other group members.
Some microlights do let you travel too; my Easter weekend involved flying from London down to Avranches (10 miles east of Le Mont Saint Michel) on Friday, back to London on Saturday with a lunch stop at L'Escale at L2K, up to Cromer on the north Norfolk coast and back on Sunday, then down to the delightful little private field at
Verchocq (about 7 miles SE of BNE) for lunch today.
Theoretically I could have done it 40% faster in the group SR20, but in reality I couldn't really have expected to monopolise a shared aircraft for the whole of Easter.