2003 Tt600, Fuel Pump Problem?

Hi everyone, new member and new Triumph owner here. First of all I apologise for starting a new thread but I couldn't find my exact problem anywhere.

The problem: My TT600 wouldn't start tonight.
I rode to work, it started normally at home and idled for a few minutes warming up. It was a warm day today, over 30°c. Temps stayed normal on the ride in.
The bike seemed to stutter in first gear at low revs leaving the suburbs. It felt like I was running out of fuel but the light was not on.
I stopped and filled up but the tank was already half full to begin with.
The stutters in first persisted but I didn't notice them if I kept the throttle smooth and changed to second as soon as I was up to speed.
I stopped again at the shops before work, and again the bike started first touch and I rode the last minute to my park.
Six hours later after leaving work, it started up first touch like normal.
At this stage I do not remember if I heard the fuel pump priming, but I think I would have noticed if it didn't. I'm new to EFI bikes but waiting a few seconds for the primer whine is already a habit. Also the digital display booting up.

While I'm putting on my helmet and gloves, the idle speed was sitting around 1500rpm for a minute and then suddenly dropped down and the bike stalled as though the petrol had cut out.
I tried to start it again, the starter motor cranked no problem and the lights were unaffected by low battery.

I let it sit for a while, tried again a few times and got nothing. Eventually I realised the fuel pump was not making the whining sound I assume is the priming stage. It usually does this when I turn the ignition on.
A bit of googling and searching on here led me to look at the fuses which all seemed intact, although some were too hard to remove without tools handy.
I also noticed the relay (the square black box under the seat near the fuses?) Was clicking when I turned the ignition to on, or possibly it was when I turned the killswitch to on.

The bike has a bit over 20,000km on it and 2 previous elderly owners who never abused it and held all the receipts for servicing. It's due for the 20,000km valve clearance check and they are a bit noisy but overall it was mechanically sound until this let down tonight. I've been taking it easy until I can get the valves done and haven't even cracked over 100km/h on it, and haven't been out of 3rd gear beside testing when I bought it.
Unfortunately it's my daily ride and mechanics are at their busiest this time of year so any ideas would be greatly appreciated.
I want to get it in peak condition and experience a piece of history! Unfortunately I'm pretty daft mechanically so I have much to learn...