I am no expert at all, but bought a steel spare as I failed to include one in my initial purchase. Reading up on it, it is recommended to buy steel bolts, but as Johnwales suggests alloy will get you home if the journey is not too long.
I agree. The skinny wheel is a 'get you to a garage fix' so we should treat the full size spare wheel in the same manner or, get steel fixings if we intend to run for a long distance like from a holiday to a local garage.
I assume that the Ford B Max is the same as other Fords in that the wheel fixings uses a 60 degree taper cone seating.
They will be compatible both Ford alloys and Ford steel wheels and therefore can be used to secure the spare wheel supplied with no worries whatsoever.
My concerns will always be:
a) The rolling diameter of the skinny spare is smaller than the standard alloy
b) The tyre width and profile are different
c) The tyre construction is different
The skinny spare is very much a tip-toe, get you home solution to be driven very carefully.
I would be far less concerend using a full sized steel spare alongside alloy wheels but would still treat it as a non standard set up and drive accordingly
Insurance companies would be ok so long as you only used the skinny spare to get you home or to a tyre fitters and you drove within the speed restrictions. It would not be reasonable to leave the skinny spare on for weeks on end and drive aboutas though you have four good tyres.
It is also important to inflate the tyre to the correct pressure which is about double a normal tyre as it is so smallbut some people may not realise this.