Good to hear, are you standing again? Have you spent time working out how to do it better next time etc?
FWIW My background includes over a decade of club and event promotion work, effectively doing the equivalent of several election campaigns a month for a decade, and frankly in comparison the vast majority of election campaigns I've seen by any vaguely left wing parties give the impression of being run by well meaning amateurs, but never give the impression of actually standing a chance of winning anything. I've also been peripherally involved in 2 piss poor green party election campaigns run by a few clueless people without any concept of how to actually run a decent campaign or any belief in the potential of actually winning, 2 lib dem campaigns (against the tories), the latter of which really did blanket the area in campaign material and won a huge majority on a largely anti-tory ticket (which obviously proved to be a false ticket, but that's another story)
Winning a seat on an anti-tory ticket is all down to the perception in the minds of the general public of the area about the ubiquity of the campaign, leafleting and canvassing are all vital ingredients, but in perception terms IMO it's the posters that do it in terms of giving people a feel for who's the most realistic anti-tory ticket. For that landslide lib dem campaign I reckon they had as many or more posters out around the area as all other parties combined, and it was relentless, with a 2 man team out for 5-6 weeks solid beforehand banging in the staked boards in supporters gardens, window posters out, and in the run up to the election there were 3 car loads out 2 nights in a row for 6 hours a night sticking hundreds of posterboards up to ensure the entire area was blanketed the day before the election and election day itself.
By comparison the local left wing campaigners (alliance for green socialism) just seemed to have gone through the motions of sticking a few boards up, with probably 100 posters in total across the area whereas the lib dems probably put 500 boards out on the 2 nights before the election alone to top up the hundreds that were already out there.
This was all achieved by a a core active team of maybe a dozen people, supported by another 15-20 or so in the immediate build up to the election, so in numbers terms it shouldn't be that difficult for the likes of Left Unity to pull in that level of active support in an area. The key difference IMO being campaigners who're determined to do what it takes to win, vs campaigners who's primary goal seems to be to avoid losing the deposit, and be able to say that they made a token effort. Obviously the national level exposure makes a major difference, but particularly at local elections it should be possible to overcome that by being seen to be the most active actually on the ground in the area.
Just my opinion of course, but if you don't set out with the goal of actually winning, then you've basically guaranteed that you never will. Start off with that goal then work out the plan of campaign needed to achieve it, and recruit the support needed to make it happen, and actually have that supporter base going out there telling people that they're seriously aiming to win it, and left wing grouplets might just surprise themselves. I doubt there's been a better time to make that sort of breakthrough in my lifetime than right now, the level of anger at all 3 parties is astonishing, and extends across a huge swathe of the population. For starters there's a good 10-15% of the vote made up of former left of centre lib dem voters up for grabs, significantly more in areas where they'd previously done well on an anti-tory ticket.