If you are studying towards a degree with the open uni, and don't already have a degree, then you are still eligible, even if you've had loans from the SLC before.
It says
"Household** income below £16,510 for a full award and £24,915 for a partial award, plus allowances for dependants*. A full fee grant is worth £805 for 30-60 points of study, and £1,210 for 90 points"
Are your courses that expensive because they are law or something? It also says
"If you live in England, Northern Ireland or Wales and will be studying a course with a high fee, for example business or law, we will top up the government fee grant. This top up will usually cover the whole fee if you get a full award or a proportion of the fee if you get a partial award. You will only receive this additional support for one such high fee course per year."
So I would give them a call to find out if your fees would be completely covered. Remember you will probably be able to get the £255 course grant also, which could help towards it.