(2-part post):
Just an example (assuming that Stansted is suitable for you);
Fly out of Stansted 0755 on Monday 15/06/09, arriving Girona at 1055. (Or fly out at 1035, arriving at 1335). Total fare (including taxes, charges & card handling fee - but assuming only hand baggage) = �46.26.
Take the connecting bus service into Barcelona. (Journey time = 1 hour 10 minutes. Return fare, valid for 30 days, = �21)
Stay at the (well-reviewed and central) Pensi�n Canaletas (listed as 'Barcelona City Ramblas' in the link below), in a twin-bedded room for �25.32 per person per night, for 4 nights. Total = �101.28.
Fly back from Girona, on 19 June, at 2200, arriving at 2310. Total fare (on the same basis as above) = �25.71. (There's an earlier flight at 1400, arriving at 1510, for �9 extra).
That makes your total, per person, come to under �200. (You'd also need to travel between the bus station and your hotel but you could take a local bus for a euro or two, or even walk it)