I think open ended spanners are just fine as long as you or someone else hasnt over-tightened the fitting already. then you need the split ring spanner.
On mk1's, Ive seen all of 7,8,9,11,12 and 14mm bleed nipples.
'91 Cabby 1.9 TD - GT-15, FMIC, stainless 2.5" exhaust, Bilstein shocks, tuned injector pump, big nozzles, BIO-DIESEL - 5.1l/100km @110km/h
'07 Octavia Kombi 1.9TDI - VNT1749VB, 2.5" 304SS exhaust, VIEZU tuned, Eibach + Bilstein, GTI brakes in Skoda Green, BIO-DIESEL - 4.6l/100km@110km/h