| Thanks guys. The trees are in a conservation area with preservation orders on them. I could take a chainsaw to them but it would cost me loads in fines.
I've tried the soapy water and scrubbing brush without much joy, perhaps because the owners manual specifically states "Never use a scrubbing brush on the roof" so I didn't exactly attack it - perhaps I was too gentle.
I'll see what BMW do | 
Jools
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