I haven't seen this episode, Rosina, as I'm American and it hasn't been broadcast here yet, but you have to remind yourself that this is
fiction. Television. The vast majority of the outdoor scenes are not shot in Hastings, sometimes not even in Sussex. For instance, there have been several key scenes in different episodes filmed at the Eastbourne Bandstand -- which obviously isn't in Hastings. This link spotlights some of the important locations which have been used in the various shows:
http://www.foyleswar.com/locations.htm. They range across the South Coast and up to Surrey and even Hertfordshire.
Why would they do this? There are a few reasons, I think.
- availability. They need to use buildings or settings which can be made available to them for shooting. This means clearing away all modern cars, closing roads, avoiding modern air traffic, and heaven knows what else. The logistics must be very complex.
- historical accuracy. There is a great effort put into finding buildings or settings which can be made to look "period" accurate -- no new buildings in sight, no burglar alarms visible, no roof aerials, etc., etc. Not an easy thing to do! Did you know that Anthony Horowitz had initially planned to set these stories in London but abandoned the idea when he realized that there simply aren't enough old buildings left to make it logistically possible? Too many were destroyed by the Luftwaffe.
- money. I'm sure cost must play a role here, too. I remember AH saying in an interview that they had found a terrific setting for one scene (a disused mine in Wales) which they couldn't afford to use, so they "faked" it.
- artistry. A set like the promenade at the Eastbourne bandstand must be nearly irresistible. It's very picturesque. Visual appeal has to fit into the equation somewhere, don't you think?
What it comes down to is that if the director finds the perfect location in another town, he will of course use it even if it is fifty miles or more from Hastings. After all, most viewers will never know the difference -- only folks who, like you, know Sussex and the South Coast well. Call it artistic license if you will, and try to make a game of spotting familiar settings.
I can empathize with your annoyance, though. I live just outside Washington, DC and am often amused by the license taken by film and TV about this town. They're always getting things wrong! I remember one television show in which a character referred to driving
east from Washington toward the Blue Ridge mountains, when they in fact lie to the
west. Head east far enough and you'll fall into the Chesapeake Bay!