This is a shame. I would imagine the only other route for appeal would be to seek a judicial review or to petition the secretary of state directly however suspect its difficult to overturn the decision of the Planning Inspectorate unless there are significant errors of judgement.
The clearly tenacious developer still has to raise development finance to build out the scheme which may not be so easy at the moment however I have read in Acorns blurb that property prices in Forest Hill are now 'higher' than they were in 2007 and mortgages are cheaper than ever before- news to me.

Re the comment about internal space standards- I assume that they still meet minimum standards even though they are not particularly wonderful?