What would a reasonable budget be?
I think it depends what you feel comfortable spending. You can have an amazing day on a low budget.
It really depends on what type of wedding you want. If you go all out it could be £20,000 or more, but if you DIY it could be only a few thousand. It also depends on the number of guests too.
Depends how much you DIY. Probably keep well under £10,000.... if your looking at paying people to do different aspects could easily be £20,000 .. do what you are comfortable with