Can anyone give some advice how to get a good deal to hire a
Routemaster for
a wedding?
Try www.timebus.co.uk
since that's more expensive that other companies have quoted me for a

My sister had them do her wedding, they were very professional and it all
went off without a hitch, plenty of room for everyone and it was definitely
a spectacle (she told the guests they would have transport, but not that it
would be a bus!)

I recall if you had an open platform you need a conductor for safety, which
pushes the cost up, whereas the one with driver operated doors at the front
was single man operated and cheaper.

Plus of course they have to spend time checking the route beforehand to
verify it's bus-friendly etc.

Cheers,
Dave