The full list of Tha consulates in the British isles is
HERE.
The regional consulates are generally a one-man operation, often run by a retired British serviceman or civil servant. Why Hull should be so favoured is a guess - maybe a lot of applicants come from the far north of England. The Birmingham consulate is equally amenable and undogmatic. Sticklers for the rules will be the consulates that employ Thai staff, and the consular section of the embassy in London. Our personal experience is with Birmingham. The advantages of Birmingham are that it is reasonably central in the UK with good train services, a five minute walk from the railway station, and the process also takes only five minutes. You can also apply by post.
In answer to your second question, the rules are perfectly clear:
1. Travelling without a visa: A return ticket is required and this will be verified at the checkin desks of all UK airports for Thai bound flights or tickets with on-going connections to Thailand. If you don't have a return ticket you will not be allowed to board.
2. Travelling with a visa of any kind: No return ticket required.
Hope this helps
