www.espdesign.co.uk do a really nice lower splitter in the style of a Aftermarket Mk6 Zetec-S Trusimo kit, but isnt really designed to be fitted on cars that are too low as you might catch it and destroy it.
RGM do some injection moulded plastic items but they are abit tacky most places do RGM as they are cheap, ESP Design stock them I think.
www.cituning.ltd.uk do alot of items for the saxo that are slightly harder to find, might be abit more pricey but thats cos they stock rarer items. Have a look and see whats available.
If you still cant find what your after to give the car that lower look then I think the only option is a full aftermarket front bumper. Have a look at places like
www.essexracing.com and
www.cituning.ltd.uk for kits.
Hope that helps