You say that Blackpool is the most depressing place you've been to. I think you'd better name the 49 countries. They might all be posh holiday destinations.
I lived in Brighton for many years but sometimes visit. Even with dollops of recent poncification it too can look a tad rough round the edges on some days. So take no notice and have a good time.
get drunk, eat fish and chips, go up the tower, go on a roller coaster, ride a donkey, build a sand castle, have a fight, watch Charlie Chester at the end of the pier and pick up a dodgy woman of the night