Woop woop, They made that extra tier. I instantly raised my pledge to 30 pounds.
I asked them whether the £30 tier includes beta access.
Their reply:
£30 tier includes insider forum access (that was a mistake, sorry), but not beta access. We created it for people that didn't want beta access but would like to keep up to date with awesome videos of the game they've supported.
You can always add a beta copy for £15 with our add-ons, however
So even though I am upping my pledge to £30, I am still in the £20 tier as I want to have access to the beta