So, you have just over two years to go ? If so, a little early to be looking at equity. For the purposes of a F&F when a property is involved, it is customary to assume the extension ( your c£3k could become c£5k in the next 18 months or so). So your creditors would be assuming collecting a further figure of around £3700 by the end date.
Usually, to reflect 3 years time and admin saved, along with the 'bird in the hand' principle, you can round the figure down a little --- but ( there is always a 'but') a monthkly payment of £91 is almost as low as it can be to keep an IVA viable, so your wriggle room is diminished. Added to which the creditors will be stung £300 - £500 for the required variation meeting.
So, all in all, you need to stick pretty close to the projected return ... maybe £3500. You might tip it at £3,000, but it would be more of a gamble. Low offers do get accepted, but high ones have been refused as well (Not helpful, I know!).
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014