Well when the ice block that was my washer bottle defrosted the jets refused to work so today I took off the front bumper and had a look. The motor was working fine and so I undid the 3 bolts holding the bottle in place and disconnected the hoses. After blowing down the hoses I found that there where no blockages so I took the pump off the bottle and then the rubber grommit/filter. I discovered that the actual screen wash had congealed and formed a kind of skin which blocked the filter when the water ran out.
I'm not sure if this was because I just used a blouse screen wash or maybe because I mixed two different types. I doubt that the ice did it but I don't know. So anyway I took the bottle into the back garden and blasted it with the hose and a brush cleaned the filter and put it all back together. It's working better than it ever did, in fact I've got to readjust the jets down because two of them are almost going over the car!
I'm going to look at getting a quality screen wash and mixing it like 50-50 with some cheepo vodka incase anymore freezing temperature comes so I don't get caught out again with no jets. If anyone else is having this problem that I had I hope this helps. And by the way I read on here somewhere that it is hard to get the wash bottle out, this is totally not true, you've just got to take the front bumper off. Dead easy!
P.S. Could anyone tell me how much the parts are for the heated jets, possibly part numbers too? Thanks.