Why £0.01?

I very much doubt it is tidying up. I think more likely somebody's idea of a joke or very frustrated with the SM. 

Having discussed the BOT question with Tim at length recently, I also doubt it is this. I suggested several possible ways that some investors may have found ways of gaining a small time advantage on the SM; however, he was able to say that he has spent at lot of time trying to prove this. As administrators of the software behind the platform, SS are able to go very deep into the data, and from this they cannot find any evidence of particular investors buying heavily and consistently.   

I have sold 1p so I can solve recaptcha, in preparation for selling between accounts.

Edit: I also think new members buy and sell pennies, just to test buying and selling on the SM.

Your page doesn't actually refresh neccesarily at the same time as stuff becomes available, (unless you have an addon that constantly refreshes the page for you, - but they can get you into trouble) sometimes the bits come and go between your browsers refreshes so you don't actually see them - they can do it very fast if it's all tee'd up. 
As for why, there's a lot of conjecture on that, considered opinion is people trying to "game" the system.  sometimes I suspect people will genuinely want to transfer stuff between, say for example, husband and wifes accounts, to balance out holdings or whatever.
HTH
Brian

@cd what is the difference between a bot and a macro

Yep a macro just repeats some chain of keystrokes (possibly with one or two adjustable inputs), whereas a 'proper' bot will collect as much available information as it thinks it needs, probably including some stuff from 'outside' (i.e. private stash of information, not visible to other users, such as how much you hold, how much you want, what is the minimum/maximum size you are willing to buy, how much exposure you have to other loans to the same borrower, whether it's raining .. practically anything! and then decide whether to bid/buy, fill in the form, and submit it. On a fast line and a modern PC you can do all that in milliseconds, and kick back a response before 'liveware' has even had a chance to read all the words. You =can= even build a bot to look at pictures, read words, listen to .mp3 files, and fill in captcha forms, but that sort of AI comes expensive, and there is not really enough at stake when buying on the SS SM to make the investment viable, except 'for fun' maybe - i.e. can you develop AI which is smarter than the one Google is using to try to trap you.

The FC bots had got pretty smart before 'auction bidding' went away - able to predict at what rate bids would come in through an auction, what the final marginal interest rate would be, and when therefore it was best to leap in and buy. Sadly they never did get very good at predicting exactly which borrowers were going to go mammaries skyward before they had repaid their loans .. 'real stupidity' beats 'artificial intelligence' every time. 8>.