Finally got the answer... the seal has two springs, one slighlty larger in diameter than the other. On the end with the larger one, the outside edge of the seal is slightly chamfered. This is the BOTTON of the seal.
And dont shoot me if it goes wrong but, dont fit the seal then try and insert the tube into the slider (leg). I did and it damaged the spring. The Haynes manual I have shows... first refill Slider (leg) with fork oil, then, Fit the metal ring spacer in Slider. Release or remove bleed valve on tube, careful with o ring. Then lubricate tube with fork oil and fit the seal (and dust ring) onto the tube, then keeping them pretty high on tube, insert the tube making sure you gently engage it with the leg's internal bushes, then when its at the bottom, you know the tube is central in the Slider. Then carefully slide down the seal, tap it gently into place, insert spring retaining clip then the dust seal. Hope this helps someone.