If you have sufficient space you would be far better having a 900 x 900 L shaped base unit in each corner which will allow full access to the corner and both doors can fully open. Trying to get in a straight corner base unit with a 400 door is a nightmare. See image for what l mean.

If i understand correctly what b&q have told you is that any 'blind' corner unit they supply, the only way that the door is hinged is from the side panel, ie the left hand corner unit has a left hand blank panel [as its tucked away under the corner] and the door is hinged off the right hand side panel and the handle is in the corner, this is the complete opposite to the rest of the industry, for any corner unit the door would be hinged off the centre post.

Looking at the b&q website they even shows the door hinged off the centre post. As 'standard' a corner unit with a 400 door would be made using an 800 unit with a 200-230 void [blanking panel and corner post]. With a 900 unit the centre post is set up for a 450 door [not sure if it can be moved as they have a top metal rail] so a 400 door has to hinge from the side panel. Again looking on their website they have corner pull outs to fit inside 800 corner units and the door is hinged off the centre post so they do have 800 corner units - maybe its an up selling technique they use making you buy their corner pull outs.

I'd go back into the shop and have a look at their displays if you have the the doors hinged the way it looks [with the handles in the corners] then you'll need 155 or more degree hinges [for easier access] and your doors could end up banging into the oven handle and getting damaged, also ask why the corner unit is a 900 instead of 800, did you ask for a bigger corner unit?

Could be you were unlucky and had a sales person who can't design kitchens

Thanks for the response, they just come back to me with the below:

“Just confirming that the dimensions of both corners are a 900mm Unit with 400mm door.

Because it's a blind corner, there is no side panel for the hinges to go on the opposite side. This would be the same for all blind corner units, and there is not adjustment with this.”

Is there anyways around this during installation? Attached is image of my other place that looks to have had wood installed to latch the hinge onto.

I think b&q are talking rubbish as its not the same for all blind corner units as your photo of the other supplier has shown, i've attached a pic of b&q own 800 base unit and this has a centre post to hang the door from, all you'd need to add to this is 1 door [with hinges], blanking panel and a corner post

or if they can't do this then there's a blind corner hinge thats available which can be fitted to the blanking panel [panel has to be the same thickness of the door] and that would work. Downside of these hinges is they're not soft close.