According to streetlightonline it runs 135W SOX. Shame I can't read the lable on it the image is not clear.
http://www.streetlightonline.co.uk/geclpsgear.htmI think its the same one as in the picture, the 90W one has more teminals on it than this one.
From Mike B's photo:
The ballast needs a series capacitor rated at 440Vac rather than the more common 250vac parallel type. Connect to terminals 2 & 5. Terminal 1 is on the left. Getting the right voltage rated capacitor maybe tricky. It looks like 12uF.
N = terminal 2, for 220vac, L = terminal 3, for 240vac, L= terminal 4.
Connect lamp to terminals 1 & (I think) 5. The only other possibility would be 1 & 2 (N), however, being a leak transformer, the neutral side of the lamp isn't normally connected to supply N. (It is however on ignitor ballasts).