Bosch dishwasher - fixable? (Havant PO9)

I bought this for £80 from someone on Gumtree, but I can't get it to work.
If you are more technically-minded than me you may be able to fix it.
It starts up healthily, making all the right noises, so the inlet and outlet pumps appear to be working correctly; but it very quickly gives up with an E-14 error code.
According to the internet an E-14 code is "fairly easy" to remedy, by replacing the reed switch flow sensor. I have done that (following the instructions on a Youtube video), but it hasn't made any difference.
Although I've now given up on it, I'm reluctant to take it to the tip. I still don't think there can be much seriously wrong with it, so If you fancy having a go at fixing it let me know and I'll bring it to you.