Thanks for all the suggestions. Saw some places mentioned I'm considering (Lincs, Margate, Burnham) but probably the most important thing I didn't mention is I have a dog. And although she won't be replaced, I'm hoping to foster. The main problem is how to find a decent landlord? I don't want to be moving every 6 months/year or so. Landlords that will allow pets are like gold dust.
As for moving from Southend, the main reason I'm here is becasue I'm on the front - a wonderful view. I wouldn't move anywhere else in Southend unless it was also on the front. I have no ties to the area and have only lived here 8 years. Friends I have made here would visit wherever I move (within reason - Northern Ireland's probably out!).
As for rent, I could get the equivalent flat elsewhere for much less rent - a couple of hundred pounds a month would be better in my pocket than a landlord's. Another drawback to this flat is the heating - or lack of. Storage heaters in the front room & bedroom, nothing in the kitchen and one of those wall heater things at the top of the wall in the bathroom which only heats the ceiling. The temperature in the bathroom in the winter goes down to about 4 degrees; in the front room I'm lucky if I get 16 degrees without using stand-alone heaters.
But it's a great flat for all that! I'm not definitely moving, but I might need a ground floor flat/bungalow one day...