I'll start by stating that I'm in Scotland so different rules / regs may apply.
I'm also in a 30s semi and I think what we might be able to do will be different to what either our attached neighbour and driveway neighbour will be able to do purely based on the aspect of the houses.
We are on a slight hill so our driveway neighbour was refused permission for a rear extension as it would affect our privacy and light, especially as their property is to the south of us. We have a rear conservatory as does two up and two down.
We are currently planning to replace our conservatory with a rear extension and I think, like you, we'd have to keep it 3m from the boundary of our attached neighbour.
Your issue with the bat survey is strange. I can't answer that. A phone call to the Planning Dept may do.
With regard to permitted development, we thought our 5m x 3.6m extension would fall within PD but the architect designed the roof 30cm too high and we need full planning (yes, 30vm! Grr!). Just be really careful with dimensions.
You also appear to be knocking down one conservatory to build another? And that your neighbour needs you to take down your conservatory to facilitate their extension? Have you actually agreed to this, in writing? I hope they are paying for the work, plus a bit extra for your inconvenience and potential loss of house value! What if you don't go ahead with your plans? What is their Plan B for their build? If you are concerned and have legal cover on your home insurance it may be worth giving them a call. I also think your mortgage company may be interested in any work that would adversely affect the value of your property.
What daylight will your potential new conservatory get if its surrounded by brick walls? Glass roofs are hot in summer / cold in winter - despite what the salesfolk try to tell you!
I would go back to your architect for advice, but I'd also be wary of a conflict of interests if they are also assisting your neighbour, especially in relation to the boundary issue.