Thanks for the helpful link. From what I can see they're undertaking to ensure that not a single disabled person would be worse off under their scheme with many better off, plan on keeping housing benefits in their entirety, intend a revised form of child benefit to similarly not leave families worse off and propose a pension scheme which is higher than BI and current basic state pensions in addition to retaining existing earnings related state pensions.
In short: they're proposing to abolish ~£37bn of targeted subsidies for working age adults but retaining ~£67bn of them. Pensions and child benefits get totally replaced, but by new subsidies that cost more than what they replace. I think this is a much better approach than eliminating all or nearly all the existing benefits as is often favoured by right wing BI proponents, but it leaves untouched or simply renames more than it eliminates, and ultimately they're proposing to balance their books far more from offsetting tax increases than by eliminating traditional targeted welfare subsidies.