Richard,
Standard ISO 32 grade hydraulic oil is available from “new” Myford – at the rather high price of £16.50 + vat + postage. The last lot I bought from Myford Nottingham in 2009 cost £7 for a litre collected at an open day.
I have just bought some, identical spec, from Smith & Allan of Darlington at a very reasonable price of £6.99 for 1 litre that included postage. Delivery was fast and the oil was well packed. They advertise all sorts of other oils on their eBay site.
I also enquired at my local garden machinery repair shop and they said they would happily sell me 1 litre from their bulk supply if I took along a suitable container – again at a very reasonable price.
There is no need to pay the earth for standard specification oil.