Firstly how fast is the engine turning over? If its slow the starter motor will probably be at fault. The fuel pressure has to reach a certain level before the ECU will open the injectors, one cause of low pressure could be that the engine is not turning over fast enough. If that's OK the next most likely problem is the pressure regulator on the HP pump, these have a filter that can clog and reduce the pressure and cause all sorts of other problems as well.

You are unlikely to have much in the way of engine wear unless its done a very high mileage, I have one that's done 200,000 miles and still starts fine. Its unlikely to be fuel starvation if it starts OK in warm weather.

I have had several engine problems with mine and they were all caused by the pressure regulator. They don't all have a filter so you can get away with removing it, this is what I did to mine and its been fine for the last year or so. You can get a used one quite cheaply on ebay or a new one for about £80. They are quite easy to fit, bolted to the pump behind the fuel filter which you will have to remove, two screws and a plug, the screws will probably be torx or allen, a 1/4" drive ratchet with the appropriate driver is the easiest way to get to them.