Equity release is debt creation. For every 1E you release in equity, you increase your debt by 1E and that debt has to be serviced. Nor can you rely on banks allowing you to release equity - so if you need the property to fund your retirement, you may have to sell the property rather than increase the outstanding debt on it.
Personally I wouldn't touch the idea with a barge pole. I'd get the principles paid off ASAP and then cash in the properties and deal with cash rather than property but then I'm not a risk taker.