diesel cold start solution

It was -15 degrees out by me this morning and the diesel rangey wouldn't start due, i think, to crystalised fuel. Apparently diesel available in the UK begins to freeze at -15 and clogs the filters.

This seems to be the best cure. I wondered if anyone had tried it:
Stanadyne Diesel Fuel Additive: Performance Formula Stanadyne all-season, all purpose diesel fuel additive, designed to tackle virtually any diesel fuel related problem

Good or bad?

or just put a gallon of petrol in the tank

Or parrafin.

We get the same (and lower) temperatures here and what I do to start my **** tank is to turn off all un-needed equipment, and heat, turn off ignition then back on, heat again and crank and to date it's always started. So far so good.