Reply From Arriva

Today I have received a reply from Arriva Customer Services and they said that it would be perfectly fine to go ahead with my plans, as long as no passengers were in shot, the bus wasn't held up and that the bus driver gives permission.

This was their reply:

This is absolutely fantastic that they were able to get back to me so quick and the positive reply is also great. I was apprehensive as to whether they would get back to me, however I am extremely grateful that they have and I have sent my kind regards.

This now means that I can go ahead with my plans to shoot on one of their buses, which means all of my plans are going as wanted so far.