eBay and Craigslist finds

It is other people bidding, because otherwise the price wouldn't be going up surely.

That's what it is, exactly.

You bid £50 max early. It shows as a £1 bid (the min)
Someone else bids a tenner. Your bid is automatically increased to £11 to beat the ten.
Someone else bids fifteen. Your bid is increased to £16.

So, the record shows you at £1, £11 and £16 (or maybe £1, £10 and £15, I'm not sure). Looks like you are bidding against yourself, but you are not, you are winning out against other lower (max) bidders.