Thanks for all the help and advice ( sjamesb3466 :thumbsup:). Going to reduce the gaps with some timber strips to the frame, and bought these in the end which should be job done for under £50 and retains a really nice old solid original 1930s door.
Got an old timber front door in a timber frame. It has perhaps shrunk over time, or was just badly installed in the first place. I tried the stick on weather stripping stick on foam stuff, but because the gaps are a bit uneven, it wasn't very successful and it didn't stand the test of time...