It has certainly been an issue for me in the past in no name tents, and even then that was on thinner foam mats (hateful things). It's all the more likely to be a problem now with the thick Exped, so the steep sides are something I'm keeping an eye out for.
And that leads me to the conclusion of all this, which is in a discussion with a dealer about either an MSR Hubba Hubba NX 2 or Big Agnes Copper Spur HV UL 2.
Steep sides for the sleep mat space, lots of head room, pretty lightweight, small pack size, only slightly over budget with discount codes, relatively robust for most of our three season weather over here.
But neither actually has the porch design I set out wanting...but what they do both have, is an add on porch tent (MSR Gear Shed which basically turns the tent into the Hubba Tour 2 and Big Agnes Copper Hotel HV UL 2). So if I do and up enjoying tenting, I can buy the extra space if/when the trip requires it, and thereby have a smaller light tent, which can be expanded as and when needed. The prices for those extra modules are all over the shop over here, so it's a case of importing from the US, but only if I actually find I 'need' them.
So thank you all for your recommendations and for sharing your expertise.
It'll be an MSR Hubba Hubba NX 2 or Big Agnes Copper Spur HV UL 2...Or a second hand Hilleberg Nallo 2 if I crumble to the gods of more weight, more money, less interior space and more pack room but oooh sturdy