There were some pictures a few years ago showing the mission bay used as a second hanger with a Merlin in it. Basically one end opened out doubling the length of the hanger. This was rather a long time ago though and I suspect it was a much earlier version of the Type 26 design.
Based on the data & images I've seen online & at trade shows the Mission bay is the top of a capital T, with the hangar being the vertical stroke.
The mission bay has a door on either side of the ship & obviously a door into the hangar. The Hangar appears a comparable size to that of the one on Type 45, which we know could accept x2 Lynx, so we can easily read across that it can take x2 Wildcat.
The Mission Bay obviously appears to be big enough to accept a Merlin, which would leave room in the hangar for another one, but the practicalities of running x2 Merlin at the same time would be a stretch, IMHO.
The RN will have an opinion of what they can & can't do with the ship & it's aircraft, but it probably won't become public domain knowledge until the ship enters service in the early 2020's / the RN share the data via their website...
SA