3 Days in Brussels during summer £75pp including flights
Skyscanner have very cheap flights to Brussels during the summer, flying from Manchester (£15 each way!) I found these ones for tuesday 30th july -thursday 1st august (3 full days) for just £30 return!
I also found this hotel close to the centre which appears to be highly rated and costs £89 for 2 nights. So in total 3 days in brussels would cost about £75pp not bad!