The seller may not know motors very well and so has misnamed parts.
Two plus two wires seems about right but doesn't say what sort it is.
I would chance it being a series wound motor as milkfloats are old and all the ones I've seen are series wound, including the 12" one I bought and the 9" one I rejected.
Both of those also had 25sqmm cable coming out of the motor frame rather then bolt studs.
Having said that it is your money and £225 is a big bit of budget.
Could you go and see it before it ends?
You would be looking for the wires to be the same size, both about the thickness of a small finger, for it to be likely to be series. If you can get a look inside then you might see the field coils, series ones are usually rolled from copper flat bar rather then fine round strands of wire.
You may be lucky and the wires are marked S1 S2, as Ken says. Mine was marked A,B,C,D.
Also, if you do get a look you should check the size of the brushes and commutator bars.
There should be plenty of comm bars (around 40-60 bars I guess) in the comm and the brushes should be big and there should be four of them (or eight in pairs). The comm bars should be about 1 1/2" - 2" long.
If I was looking for a motor I would go and have a look and take cash with me, if it doesn't sell then negotiate the price down.
My main concern would be the drive end cap. It looks to be slightly domed shaped and that could make it a little more difficult to mount to an adaptor plate. It would need to be machined to give a flat area for location but that isn't a deal breaker if you are having machine work done anyway.
Good luck with it. I won't bid against you.