Hi Nigel
If I recall correctly, the easiest procedure for those nuts is as follows:
1. Get into a really uncomfortable position so that your fingers can just touch the top of the bolt. This will have to be done by feel alone as you have no hope of actually seeing what you are doing.
2. Carefully balance the nut between your fingers and locate it on the tip of the bolt.
3. Swear when it falls out of your fingers into the narrow groove. Retrieve it with some difficulty.
4. Repeat steps 2 and 3 for some time.
5. Eventually you will be able to thread the nut onto the bolt by hand. If using a nyloc, you won't get it very far.
6. Swear as you realise you forgot to put the washer on first. Undo and then repeat steps 1 to 5.
7. Again by feel alone, locate the correct size spanner onto the nut. This may take anywhere between several and many attempts.
8. Move the spanner by a few mm within the groove to tighten the bolt an infinitesimal amount.
9. Repeat steps 7 and 8 until you are losing the will to live.
10. Jobs a good un.
11. Repeat for the other side.
Hope this helps
Tim