Despite the problems MSO seems to have had with updating the website, the event looks like being the best for many years. Central London location and in an attractive venue. Also new multiple-games competition: 1st Abstract Games Championship.
It's not cheap. You can however attend for free as a spectator/visitor and play games with whoever happens to be around and available to play. It only costs if you want to enter competitions. I'm not part of the MSO company - but I rather think they do it more for love rather than money - so the prices are to cover the costs.