In article , Draven
writes

I'm in the West (Bristol) and would like to expand the question.
How much would a LARGE company expect to pay a gardening contractor to
maintain the company site?

Well, here's a radical thought...

Why doesn't someone in this LARGE company get out a phone book and ring
around a few gardening contractors and ask them to come and give a quote
for maintenance. It isn't going to cost you anything to do this, and it
takes away what can at best be expected by any urg inhabitants; vague
guesswork.

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Flower Bobdew
South Facing Garden
South West: UK