Hi Robert
Push a couple of lolly pop sticks down to opposite sides of the hexagon and eye them up until they are parallel, measure the gap at the top, you should be close.
Then search (eBay etc.) for an old fashioned box spanner to suit, if it's still to short go down to your local steel fabrication workshop on a Saturday morning ( most small outfits do 'homers' on Saturday) with a bag of donuts and a tenner and ask them to weld an extension on it.
Failing that, get a standard socket, of the correct size, cut the square drive part off it and get said fab shop to weld a a piece of tube to it.
If it takes you 3 tries you'll still be well under the £180 budget!
Cheers
Stef