Here are directions :-
Coming from Glasgow, pass through milngavie and take the road for Strathblane ( A 81 ).
The reservoir will be on your left.
You will pass some new build houses on the right ( somebody is building new houses )
Then you will pass esporta sports centre on your right( careful ! there is a speed camera here)
Take the second driveway on the right after Esporta. This is signposted Bankell farm campsite.
Carry on down the narrow tarmac road to a junction at some farm buildings and turn left.
Follow this road around the farm buildings to a car park.
We are down the embankment behind the car park.
Here is a link to a map (I hope!) Bankell farm is at the end of the dead end road just showing at the start of Craigmaddie reservoir.
I have been there once for HFT not too hard to find.