The tricky side next to the deck is done, the minimum tomorrow is all the 3 sides done(leaving the filter side until everything is done, and start plumbing the filters in, if it gets done tomorrow, fill and PP the system, personally I don't think it'll get that far but it's getting closer.
Strip it all down again tomorrow and find if it's the bottom drain its self or the pipework, pipework is good, that can be fixed, the bottom drain could be a problem but again probably fixable, please remember this is a second-hand system, problems were expected, the window for the fish will be closing in less than a week.. if I miss out this year I miss out, at least I can add the shower at my leisure.
It's the bottom drain :-( Got it all stripped down and on breeze blocks, added a bucket of water and it was just pouring out of the seems of the drain. It's not as bad as it sounds as it's only leaking in 2 places but there is no point patching this up, the previous owner had gone for the mass silicone approach on an uneven surface, is probably only held as they did it once and never moved it, this has been stripped down and transported then reassembled with new pipework it was always going to be a problem. The new plan, get some proper sealant(silicone is fine BTW, gold label is just better and 4x stronger but it's not cheap) and get it resealed and take it from there.