It's Manchester, right? There's a section, maybe the 3rd quarter, where there's hardly any crowd. The first half, and the end, there's good crowd support, including plenty of kids with sweets.
Personally I'd want my own gels, and definitely my own music. I wouldn't be fussed about a change of t-shirt but that's me (and remember if you think you're going to change your shirt, then put your race number on your shorts).