I was on Pension Credit, with no assets, when I started my divorce in autumn
2008. I went to a solicitor and he did the whole lot on Legal Aid (called
something else now but I can't recall). It didn't cost me a penny.
I don't know if Income Support is a qualifying benefit for free legal
assistance. Your best bet is to go into a solicitors and ask.
If there are no assets to split then it's just paper work and court
costs. See if you're on the right sort of benefit to get the court
costs paid for.
Of course if your missis doesn't want to get divorced she can avoid it
for a few years.
The paperwork isn't that complicated and you can get a half hour of
free legal advice even without asking for legal aid.