Turn signals not required but if they are fitted they must work.
Speedometer required.
Vehicles over a certain age are not tested for emissions. I'm not sure how old but our old bikes don't get tested.
There is a noise limit for bikes, I think the pipes must have some sort of standard stamped on them. I don't know how Hardleys get away with it. If your pipes are too noisy they will attract the cops because they need something to do except fight crime.
All vehicles over 3 years old require a yearly MOT test.
Ah, you need both front and back fenders/mudguards. I don't think it matters what size they are though.
That's about all I can tell you....oh, bring a brolly.