I ran Manchester last year, the pacers carry quite a large flag -like a sail, you are 'supposed' to wear the extra number on your back but i didnt see many people wearing them so just loiter with the group you can see the flags from a distance so If your times then slip back or forward either do your own thing or join the next pace goup. HTH.
Mine is the same age and has started to fog up since the start of this year. I think it's past its best now. Not happy dont want to buy another. Would Garmin look at a 5yr old watch? I will try the airing cupboard first.
If struck by a sudden rainstorm, remember to keep testing your brakes well before you need them !!! Also avoid wet manhole covers in the road, and dont ride so close to the kerb that you ride over the grids, especially those with missing grid covers or say goodbye to your wallet!