I bought a 3kw emersion heater when I first started wfp(2004) and used it a bit the first winter, and have just pulled it out again. It cost me about £200 then, but you can get them much cheaper than that now.
3 problems, at 3kw they use a lot of electric
I have blown a number of extension leads with it
and if you leave them on to long the ibc tanks begin to sag.
But they keep the garage warm and also when the warm water is pumped into the van, it also keeps the van warm.
Should have started to use it earlier, maybe could have done a bit more.
After thawing everything out, got to work about 11.30 today, couldn't get the microbore to work, 1/2" hose worked but had to clean an unheated consv and it just froze solid, so gave it a miss.
Thankfully some cheques are starting to be delivered by postman, so had something to put in the bank, first time for quite some time.
If still bad next week, will def heat the water up, but those hot machines are looking more attractive evryday.Maybe get one instead of contributing to taxman's bonus.