I would certainly wait till your 26 Lee, if thats possible, as it opens up the entire scheme to you.
Extending your lease to 4 or 5 years is an option but the criteria changes every now and again. In our case we were allowed to extend to 5 years as we had paid more than £2.000 AP. In 3 years time this could have changed.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.