mate - even if it did come with a warrenty I would eat my own man juice if it would cover a cambelt failure.
the warrenties you get from manufacturer wouldn't even cover camblet failure I suspect, let alone these second hand dealer warrenties - they're not worth the paper they are written on.
if its something you are concerned about negotiate it as part of the deal to have it replaced before collection - that way you have complete peace of mind. remember you want the camblet, possibly balance belt depending upon which engine it is, aux belt, tensioners and water pump all changing. expect a bill closer to £500.
the [revised] camblet intervals are around 36k or 3 years, which ever comes first if I remember correctly, so either way you look at it the car is due a cambelt.
some people have managed to go to the original camblet interval of 72k but I really really would want to risk it that far at all, stick to the revised schedule religiously.
if you are worried abotu making it home take a couple of bolts out the cover and take a look at the state of the belt for yourself, if its looking frayed anywhere or peices of belt rubber missing from any part of the belt, don't even drive it or start it. same if it looks really badly perrished.
if its sat right on the outter edge of the cam pully cogs thats another sign its read for changing pretty soon as well.
no one will be able to look at it for certain and say "yes - its got 10k left it in" or "no change it now" with complete certainty so you have to chance it slightly am afraid.
if you are worried and don't want to drive it a great distance home, post and ask for a recommended garage in the area of the sale and someone will probs be able to recommend somewhere you can take it.
its worth leaving the car with a garage for a week and picking it up weekend after knowing its fresh and ready to go than bricking yourself all way home if you worried!
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso