Here is a site that will recognize the model names http://www.partstree.com/parts/
Put Toro in the 2nd box and the 220-4 or 108-3 in the 3rd box. Then you pick the correct one from the results. Your tractor should have a data decal with the long model and serial number on it.
Another way is by using Toro's reverse look-up at : https://lookup3.toro.com/partdex/index.cfm?adv=yes&xCaller=Toro
In the fourth box down, Product Name, put what's on the side of the tractor, 220-4, 108-3, 312-8, 520-H, Commando, etc. That will give a list and parts breakdown on all of the models with that name. There is more information you can add if you get too long of a list to narrow it down. I've saved that shortcut to my favorites.
i see you're in the UK. We didn't have the 220 series in the US but they look to be a hybrid of the early 200 series (B chassis) and the later 250 series. I have no idea what your model number would be, but it will be something like this:
B1-10B401 or B1-10K401 or something similar.
B1 could be B2, B3,...or even E1, E2...
10 = 10 hp (I'm guessing this from the 220-4 name)
B = Briggs
K = Kawasaki
4 = 4 speed peerless
01 = version
I'm guessing on all of this, but I'll bet I'm close and perhaps if you plug and chug you'll find something.
Look either under the seat on the fender, or on the "tower" that has the steering wheel/hood stand for a white tag.
We had the 108-3 here, so if you do Buzz's reverse lookup you should find something on that one.