Need to get one for a stay of 8 months or thereabouts.

Enter Thailand 17th May and exit 20th December

I have 2 previous non-o visas from Birmingham and Hull in my passport - last year and the year before - I am under 50.

flight booked to Vietnam in August for my first visa run.

When should I send off for my visa and does it matter if I send it to Birmingham or Hull?

Wouldnt matter if sent to Cardiff Birmingham or Hull. They all handle postal applications and I would suggest you send a minimum of 14 days and ideally 30 days before travelling. Check there websites or call them for processing times to be certain.

Edited April 18, 201214 yr by CharlieH

As visa will only be valid for six months from date of issue (last entry made six months later or before) base your application on that.