Hi Cubic Yard,
We've just been down this route with the planners. We were limited in height also and I was adamant that I wanted to go into my attic - I just can't stomach have a void up above my head and not having access to it -if only for the occasional visitor.
Anyway, we're going to cut into our site - just a little but enough to comply with the conditions. Have you actually got you planning permission yet? If so, can you provide alittle more detail and I may be able to help. What size is your house? What size and level is your site (I ask that because if you have a reasonably large site, you may not even notice digging down 50-70cm.
Also, I got a contour survey done by an engineer - pain on the wallet but felt better after I saw the results - means we only have to dig down 30am on one side - large site so hopefully it won't take from the house asthetically.