I asked my GP for some more Diprobase, but was refused as my NHS area's formulary no longer lists it. I remembered a nurse using Fifty:50 so asked for that, and it was allowed.
The formulary now lists Epimax as the first choice alternative to Aproderm, Aqueous cream, Aquamax, Diprobase cream, E45 cream, Oilatum cream, ZeroAQS and Zerobase.
Hydromol cream is still listed, and is the formulary's preferred alternative to Zeroderm.
Isomol gel is listed as an alternative to Doublebase gel and Zerodouble gel.
The Fifty:50 I got isn't listed, but the British National Formulary has "Liquid and White Soft Paraffin Ointment, NPF", which is the same stuff (50% liquid paraffin, 50% white soft paraffin), at £4.57 for 500 g.
Diprobase in the 500 g pump pack is £6.32.
Hydromol cream (still listed by my area's formulary) is £11.92 for 500 g (yet Zeroderm, which it's meant to replace, is £4.10). Hydromol ointment (which I use as a soap substitute) is £4.89 for 500 g.
Isomol in a 500 g pump pack is £3.99.
Epimax (the now-preferred choice) is £2.49 for 500 g.
I don't know how these prices relate to over-the-counter prices for those who buy their own supplies. When I had to pay for my prescriptions, the first time I was prescribed Diprobase was in a 50 g tube, which was an absolute rip-off (ignoring the argument that it helps pay for the NHS). I then bought my own for a few years, but the cost meant I didn't use it every day.
I wouldn't recommend the Fifty:50 -- it can ruin clothes and bedding, and is a fire-risk!
I trust that Epimax is a worthy successor to Diprobase when I get to try it.