OP here -- thanks to all, in particular to Road Hog: yes, if I'd had
your post _before_ the operation then all would have been well!

No, not put off doing it again: keen to have another go, better prepared
as I now am!

The hire company should provide a copy of the basic operating
instructions with the machine -- they themselves knew nothing about
operating it. And it cost 62 quid plus VAT for the day!

Thanks again
John