Based on the assumtion that your 135 is a diesel, any good brand of diesel rated 15/40 (such as Rotella) would do just fine. (Gas/petrol powered 135's are supposedly almost non-existant in England from all I hear) I use Pennzoil 15/40 in all my diesels, including my '71 MF150 which uses the same PErkins AD3-152 3-cylinder as your 135 will have.
I could line you up with a vendor who carries turf tires here in the US, but shipping would be a killer! I'm sure there's a dealer SOMEWHERE in England. Try any full line AG tire dealer. They should be able to put you on to some.