If you want to do on the cheap, Hellfrauds sell Coma shite (still better than any Castrol shite) for around £20 for 5l. Personally I like Fuch Titan 4000, but around £30-40 for 5l.
Needs about 6-8l, depending how good a job you do of getting it al out.
Do you hate everything? 
Hellfrauds aren't so bad TBH. Somewhat frustrating if you want a fanbelt, but all they seem to sell now is Pink shite, overpriced satnavs and pushbikes. Thats just the nature of what they have become. Like trying to buy some oil from a petrol station that only sells ready meals and veg. Or trying to buy electronic components from Craplin.
I feel there is a difference between the Coma ATF and the Fuch one, having had both in my cars at various points. Not a massive difference in price, bearing in mind how often you change it.
Castrol, like Michelin, do not make a product that is suitable for anything or anyone

. But they were exceedingly good in marketing it
