Wow I don't have any of that! How much would the tube levers, multi tool, chain repair and pump set me back do you think?
Think I got my chain tool from Asda for ~£4, it even came with some quick links too. I just use the tire levers from a
Halfords puncture repair kit (I believe they're glass-nylon reinforced, or atleast they used to be, so half decent) which you can get from between £2 to £4 depending on the size of the kit.
I buy the "LifeLine" branded tubes off
Wiggle.co.uk, which are around £5 for a pack of two, or otherwise tubes are around a fiver each in town. I believe Halfords sell the Topeak Pocket-Rocket pump for around £18 to £20 in store, but I spent a bit extra and got the Topeak Road Morph, which I find much easier to get up to full pressure with.
Multi-tools start at around a tenner, but it's not quite so important to have if there will be other riders around (and it's worth considering, would you know how to use it if you did have a mechanical issue?).
The most important stuff to have is the stuff required to fix a puncture, as that is the mechanical you're most likely to have. And be sure you know how to use it! Obviously prices will vary depending on whether you're shopping at a chain store, LBS, online etc - but the basics don't have to be too wildly expensive.
To be honest, you don't even need a saddle bag to begin with. Phone in one pocket, small lock in the middle pocket with keys, and innertube and tire levers in the final pocket. Pump goes on the frame with the included mount!