If you're taking the 10-20 _and_ a standard zoom, the 16-45 doesn't really offer much over the kit lens for f8 shooting. Of those I would take the 18-55 WR, primarily for the extra reach on the long end: since the Sigma isn't WR you need to take some sort of waterproofing mechanism anyway (ie a freezer bag with the bottom cut off), so the WR isn't actually that much of an advantage.

The Retrospective's rain cover is even more of a faff than the one on my Lowepro - by the time I opened the bag and took it out the gear would need to be WR . The Tenbas do look nice, but put me into the same dilemma over size as the Crumplers.

I see from the second photo that the 12-24 has a 77mm filter thread. Since my widest lens (the Sigma 10-20) has the same, it looks as if the Hadley Pro would be useful. My only concern (aside from the cost ) is that the description on Billingham's website mentions the "waterproofed back pocket", suggesting that the rest of the bag isn't. Bit of a problem in the land of sudden downpours!

To cut what would probably be a long and interesting ramble short, I've decided I need something bigger than my Crumpler Muffin Top 4000 (tiny, carries two normal size lenses and the DA35 Limited at a stretch) but smaller than my Lowepro Stealth Reporter D400AW (enormous, holds everything, weighs more than the moon). Can anyone suggest something to hold my intended 'walkaround kit'?:

(*)Sigma 10-20
(*)DA35 Limited
(*)DFA50 Macro
(*)DFA100 Macro non-WR (in Samsung guise)

I've been thinking of the Crumpler Messenger Boy range, but have absolutely no idea which of the sizes would be best suited to what I actually want to carry. Help would be greatly appreciated!

PS: Having a small amount of leftover space is OK: if this 'primes + 10-20' walkaround malarkey works out then the money I was going to spend on a 17-70 might go on something like a DA70 instead.

PPS: Almost forgot, whatever I end up with will be a messenger-type bag. I'm aware of the pros and cons of backpacks (etc.) but I just prefer messengers.

I think this is how EVFs could be sold to the 'purists': "see what the camera sees, not what a mirror box does". I'm not trying to denigrate the advantages of an optical viewfinder, but I wouldn't jump ship if Pentax came out with a K5-E (in other words identical camera but no mirror box and an EVF instead).

All the schools with undiscovered asbestos should be the higher priority methinks

I would actually have the Sigma 10-20 over either of those (or the DA 12-24) because at ultrawide lengths a) Wider is more versatile and b) Zoom is quite useful, If you'd rather get a prime, then of those two I would personally take the DA15: f4 is fine at these focal lengths, since you can get away with quite slow shutter speeds. The DA15 is much more compact compared to the DA14, which (along with IQ) is after all the point of a prime!

Leaving aside the cost issues for businesses (what about the extra insurance premium for having cash on the premises?), I always pay with a card and if a business doesn't take them (or has a minimum transaction value) then I go elsewhere unless I happen to have cash on me.

Cash isn't safe (a stolen card can be cancelled, stolen cash can't), and it's not convenient: it rather defeats the point of giving my business to the corner shop near my office if I have to walk half a mile to a cash machine first.

Pentax have (or rather had) a medical division, which IIRC included eyeglasses. Perhaps these have now been rebranded as Hoya?

The distortion at the wide end doesn't bother me much - it never bothers me with the kit lens (which has about the same distortion IIRC) and on the odd occasions where it would matter I can always use the longer end of the 10-20.