Thanx for the advice guys!
@jeebow - yeah mate it did try to tick over but it just wouldn't fire up. I had all electrics working, the dash lights came on and went off as usual when turning the key. Also it has 124k on the clock (its going through a mid life crisis I suspect

)
On saturday I bought a brand new set of glow plugs as the old ones didn't look too bad, but also didn't look like they had been changed since the car went into production. Went to fire the car up, expecting everything to work, but... still the same... tried to start it and again the engine just wouldn't fire up.
Last result (and I wish I did this sooner) was call out the AA. The chap came over, had a look at the engine and from first inspection said it could possibly be the Fuel pump (Major ££££££

). He hooked his computer up to the ECU and did a bit of fault finding.
After all that it turns out it was the Camshaft Sensor (the one mounted on top of the rocker cover). So I bought myself a new one for £30 and now it starts first time, every time and now I'm a very happy bunny
So if this does happen to anyone else, make checking the Camshaft Sensor one of your first points of call, as its a relatively cheap fix. I would also highly recommend the AA, the mechanic that I saw was highly professional and knew exactly what to do