Olly’s described what I had- flashing glow plug light, also tach needle stayed in the position it was in when it cut out. Mostly happened under power so that fits too. Mine was a TDDI so not identical but a lot of the issues are shared. That was crank sensor, a very easy and cheap fix
Whereabouts are you? If you’re Edinburgh-ish I’ve got a fault code reader that’ll fit your car…
(If you’re halfway skilled and own a laptop (or a really long USB lead!) it’s a really good idea to get yourself a fault reader- the fsuper software and USB lead is superb, means you can read the codes yourself which can save a lot of hassle. Mine’s saved me hundreds of quid)
(Or, sometimes, it will tell you nothing useful at all- mine throws codes for “You’ve blanked off the EGR valve you bounder” but never gave me a code for “The turbo just exploded”, “The number 3 injector just completely filled its piston with diesel” or “The MAF sensor is senile”)
Actually I just picked up a wee bluetooth OBD transmitter which works with an android app called Torque- I haven’t used it yet but it’s cute and is supposed to be decent as a code reader. Very cheap.