Easyjet or Jet2 or others into Belfast International Airport and airport bus to Belfast centre for a fiver then train to Bangor for another fiver. Other flights into Belfast City Airport, BE, BMI Baby etc even closer, or ferry -Seacat, Stena HSS, Norse Merchant etc into Belfast. Bangor is full of guesthouses, hotels, pubs etc, some mad Bradford guys even camped last year. Check out the Ferry/ airline websites for details of travel costs.