Ok so i was just going back through my receipts and photos, i now know why the front seal was leaking...
Ok so i got a TD42NA to TD42t conversion kit from EA - this shows on my receipt a TD42 REAR MAIN SEAL & "FULL GASKET SET" When i looked at the gasket set (full gasket set) the photo clearly says TD42t ... The front harmonic balancer on a TD42t is larger in Dia than a std TD42 - and thus the seal that i got in my full gasket set is a different size front seal to that required... I didnt pick it up, till now.... Fark, what a twat....
Anyway this is a heads up for the next guy that does this conversion, your rear main seal is correct but if you get a full gasket set for a TD42t you will need a different front seal as the TD42 is smaller Dia.....