No start after replacing temp sender

[BlueBus88]

Hey everyone - amazing club you have here.

Quite new to this but coming from an 11 year affair with a Nissan Vanette so go easy on me.
T25 1988 DG 1.9.
New purchase so not sure of history but pretty good condition vehicle with recon engine fitted 5 years ago.

Ran almost perfectly first time (almost 100 miles) although did have a moment when it wouldn't start right at the end of day last saturday ending in a lot of traffic but this went away after a couple of minutes and the engine seemed fine again - thought it might have been too hot to start but wasn't aware there was such a safety mechanism. Fan is working.

Anyway...

Replaced temperature sender two days ago as I hated not knowing how hot it was running, especially in this weather. It was a type 2 (I think) sender with silver cylinder to go into the thermostat. On replacement, it worked and gauge started moving up - happy days - but upon topping up coolant, sender dislodged and I lost a lot of coolant (managed to get sender back in but not without getting a lot of coolant down my arm - lost a good few litres.

Replaced sender (properly now) and topped up coolant as per Simon Baxter's instructions and now it won't start.  It actually started without the sender in place to allow me to move the van a couple of metres to find the O-ring on the floor so I am guessing the sender is not critical to the van starting although I would have lost all the pressure. 

Just topped it up with almost 4 litres of mixture to correct levels and it won't start.

Turns over fine, something just not taking almost like there is no spark. Anything obvious that could have happened in this process?

Thanks in advance 

[Mr Bean]

Remove a spark plug and ensuring the body is grounded, get someone to spin it over on the starter to check the spark. That should answer that question.
Then it might sound stupidly obvious (on my part ) but does it start and run if you disconnect the sensor (electrically) as before that is ?

[BlueBus88]

Mr Bean. I'll try both these things. Thanks

[BlueBus88]

Turns out it was the connector between coil and distributor that somehow must have come dislodged in the described process. Thanks for your help