The plane came from Argos and would appear to be made for the Argos group.
Argos cant and dont supply spare blades, I came across another Person who is having the same trouble.
A conversion Kit can be bought to accept standard two sided blades for £11.
Tried Solent Tools and no joy there.
It would seem Challenge are made for the Argos group with no back-up spares as models are changed frequently.
Thanks all for your input, if I find a remedy to this I will post back.