Again I thank you all for your input.
I believe most of us are of the opinion that conditions imposed on self builders cannot effectively be enforced.
The contribution by 'Temp' of this forum encapsulates the problems.
A 'non-business/legal' friend advised that an amount of the purchase price be returned by the site developer/owner to the plot purchaser when all conditions had been completed within the agreed time scale. e.g. plot price £100k return £10k, or similar sums.
In thanking him for the input I said when/if the £10k was refused, there would be potential for a messy/lengthy legal fight.
Perhaps a number of conditions are of limited importance but such as a build out time as a condition is very important.
I fully accept that most self builders will complete their build in a relatively short time as it is to the advantage of the self builder to do so.
However there will always be, albeit limited number, of self builders who even against their best endeavors will allow a partially completed building shell to stand within a community.
It would be good if some of the LAs who became "Right to Build ‘vanguard’ councils" accepting various amounts of tax payers money could show how they are answering this matter.
Perhaps; legislation albeit with great difficulty, could be written to give an answer to the problem and written into the NPPF.
I do look forward to "Right to Build ‘vanguard’ councils" joining this discussion with their best advice on how they control the conditions such as build out time.