Mitsubishi L200 engine turning over but not starting.

Just before the problem occurred hadn't used the car for couple of weeks then it struggled to start then problem occurred felt like a battery was dying then changed the battery and it started as if that was the only problem next day it didn't start again and ''water in fuel'' light appeared (hadn't noticed that light before) drained the water from the filter by unscrewing the nut at the bottom of the filter then took the air out of the system using the manual pump on the top of the filter and the air releasing nut on the filter housing but problem didn't solve then I changed the fuel filter and bleeded the air out again but still not starting... also noticed the ''fuel in filter'' light is remaining on when I try to start it.... can anyone help with the problem ?! many thanks in advance.... in next couple of days time when I have time I will try to check the fuel existence at the top of the injectors... the glow plug light seem to be coming on and going off after a while so presume they are working fine but will check them again to make sure.... Sometimes last summer while driving on M1 I had a similar problem stopped at service station for 10 minutes and the car wouldn't start... got help from some people pulling the car in the car park to hopping to start it and it wouldn't... called AA and they couldn't find any problems with it and brought me back home... it felt like an electrical problem and checking starting relay etc. I discovered the 20 amp slow blow fuse (one of those unusual top part closed Japanese style fuse ) was blown didn't have the same fuse in my stock and just used an ordinary 20 amp fuse with an adopter and car started as if nothing happened and has been ok since...