looking at visiting the Aland Islands for a weekend at the end of August ...
best option for decent priced flights seems to be with ryanair STaNsted to TaMPere, departing London on the Friday at 18:00 arriving into Finland at 22:40 - and then spending the night in Tampere.
then on the Saturday, getting one of the regular trains to Turku ... and then in the evening, getting the ferry departing at 20:15 and arriving into Långnäs at 00:40 - and then spending the night in the Aland Islands.
after the Sunday morning on the islands, getting a different ferry departing at 14:25 and arriving back into Turku at 19:55 - and spending the night in Turku.
finally, on Monday getting one of the regular trains to Tampere, and getting the flight departing at 23:05 and arriving back into London at 23:55 - with the last Stansted Express train departing at 01:30
the flight cost is approximately 118 gbp, with the ferries, a very reasonable 10 eur each way !