There are more disused toilets in B, D and E. One of these spaces is being used for Guard's equipment such as detonators etc. One of these spaces is only present on the 5 coach train. But it should be possible to convert an additional space for 2 bikes on every service if someone is willing to pay for it.
Moving away from the bike question (and sorry if this was answered 35 pages ago) - do we know why HSTs in Scotland are considered to need fewer toilets per passenger than elsewhere?
(OK, fewer toilets per car. Granted that's not the same thing, but even compared to GWR high-density there can't be only half as many pax now...!)