I've one of the early Kodak digital cameras (a one megapixel DC120 from 1997) and it can be tricky already finding a program to open its raw files. The only solution was to hope the software that came with the camera would still run on a current PC (fortunately it did.)

I know what you mean, but why not get a used one? I've got a used Pentax 18-250 which cost around £200 and I couldn't resist then getting a Tamron version, used but mint in box for not much more than half that. There are bargains to be found.

The difference from 55 to 70 isn't really that great. It can be achieved by cropping even. The 18-250/270's aren't bad!

Megapickles: might be common:

http://www.thephoblographer.com/2013/07/01/sonys-new-smartphone-camera-may-have-...

http://theshutterbugs.net/2013/01/06/digital-megapickles/

Then there's the T-shirt:

http://www.zazzle.co.uk/megapickles_t_shirts-235053063670222629

Just had a Google search and it seems they are only available from the US ebay site. How odd.

Sounds like your current lens lineup is fine then.
If you wish to expand, try to think whether you need more reach which will require a telephoto or if you are struggling to get everything in which means you'll need wider lens. It might not look much different numerically but the extra degree of the 17-70 compared to the 18-55 does make a difference and there's a little more reach too.
Whether to go for a Sigma or Pentax depends on what you read. I doubt many users would have both to give an independent comparison. To be honest, I doubt there is much difference in day to day use.
You really just need to decide wider or longer rather than 'better' as the 18-55 is not a bad lens by any means, especially when compared to similar offerings by other better known marques so maybe a lens offering quite a bit wider or longer rather than something similar might prove to be a more useful purchase.

Ricoh's new Theta 360° camera was shown on the Gadget Show tonight (New Years Eve.) They didn't rate it very highly and said the picture quality could be better. Has anyone actually tried one for themselves? I've not come across a post on here about it other than pointing out it was available.

Fabulous!

Out of date image has returned!

They are both really nicely seen images and work well in black and white. If there is any criticism it is both have a lean to the left, particularly #2. Maybe the horizon level is off in your K5; it is way off in my mk1 K5 too to the extent I cannot use it at all. A bit of horizontal correcting in PP should easily sort that out.