i sympathise with you i had the same problem on an 81 bedford van for such a small job it's certainly frustrating. i used to hold the cup with vice grips and then push like buggery you only need that little start and then your away you'll get it just a ba$$rd of a job.
EDIT: just looked at what you're up against atleast on the bedford you had access! maybe you can still get the vice grips in there sideways using the hub as a lever? worth a crack!
After struggling with access I bought a dirt cheap pair of pliers and attacked them with the angle grinder to thin and narrow them down.
Access and room to work isn't the issue that I'm coming up against. The problem is that whenever I turn the cap to the spring, the bloody pin rotates as well. Pushing with all my strength on the head of the pin located in the backplate of the disc housing won't stop the pin turning with the cap, as there simply isn't enough 'grip' to keep the pin still.
The only way that I can see to solve this problem would be to drop a spot of weld over the head of the pin, securing it in place to the backplate. I'd have done this already, except for the fact that I don't have a MIG welder

I agree that it is dam frustrating. it should be a two minute job to get the cap / spring / pin located and locked in place. So far I've been at it since around 12:40 this lunchtime, but to no avail.
And on that note I've admitted defeat. Got a mechanic mate of mine popping over in the morning to have a look. In his own words, "I've done thousands of these over the years. Sometimes easy, sometimes not." I've told him that there is a case of Becks in it for him if he manages to do it, so we will see.
When I did the N/S handbrake shoes I was at it untill 02:30 in the morning. I simply can't be bothered tonight, so I'm calling it a day early, and am going to have a bath, dinner with the wife, play with my daughter, and then a an hour or so playing on the computer.
Thanks for the tips guys

I'm just glad that this is a job I should only have to do just the once on this Omega.