I did see mile markers for miles 1, 2 & 3, but wasn't looking hard for them as I had my Garmin. The mile markers I did see matched my Garmin almost spot on.
I would hope the organisers make sure there is an explanation & apology; openness about the issues is always best at these times. Any excuses will only make people more annoyed & less likely to return.
I have to say I was surprised that the fun run started at the same time. However, I am relieved to see photographic evidence that the person dressed as a banana who overtook me was only doing the fun run.
I measured 5.39 by my Garmin. Someone told me that the winner actually did 10k, but no-one else did - he entered the park in the lead, and left in 3rd place, but the 2 ahead of him had done the short course.
I started at the back and didn't feel crowded; first mile was 9:55 and I was mostly being passed rather than being held up. I did get my number posted to me, and I didn't feel the organisation was bad, apart from the obvious bit! No queues for the toilets in the town hall was a pleasant surprise. Parking at Sainsburys was convenient & easy. I didn't partake of the water, so can't comment on that. Muller is a very high standard to live up to. I'd run it again; I would like to think the organisers might give us a discount on next year as some kind of compensation.