I have a Lowepro vertex 300, huge and carries all my gear, but weighs a ton and holds the tripod externally, so you'll look like a 'tog. I use it for those days when you carry a lot a distance, and for weddings to keep all my gear handy and stored for quick access.
I also have shoulder bag style crumplers, various sizes for carrying different loads. Nowhere near as practical, but much more stealthy. They aren't as good at keeping your gear in place securely, but i use them when travelling.
I'll be selling a lowepro computrekker AW if it would suit, looks like a normal rucksack with the tripod carrier concealed and you can fit coats and things in the laptop compartment and to the bungees. £60 would do it.
Best compromise i can think of is a decent sized daysac with side pouches for spare lenses and extras. But your gear will be rattling about in there…