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Just an update. Tried siphoning out and 'blasting' with a hosepipe several times, but still didn't work. Main problem was getting the siphon pipe round the odd shape of the bottle! Had a word with a 'mechanic' at my local Ford's and he said if you can get at the pump, its only a pushfit into a rubber grommet at the bottom of the tank, so easy to remove. So today I removed N/S wheel and all screws at front of inner wing. Could see bottle, but had to undo the various screws holding the 'under tray' to the bumper. Why use 4 different sorts of fittings?! Anyway, left the ones on the drivers side in place so didn't lose position of under tray totally. Could access pump easily (its only one pump with 2 pipes coming off it). Wiggled it out easily . Stuck my finger in the rubber grommet to see if blockage was obvious. As its rubber, it sort of seals again when nothing is in it, so to keep it open I put in a 2" length of 12mm air hose from my truck. Flushed it through a couple of times and loads of black gunk came out. Put the pump back in and hey presto!, everything works! So if anyone else reads this in the future, you just have to undo the under tray fittings for access, no need to touch e N/S inner wing.