I am also in Devon and my experience mirrors yours. In short my cabinet was on the FTTC enable list as confirmed twice in emails from BT, with dates "...in the area of third quarter of 2012 ....". I produced business expansion plans on that basis ( Home based media business). Before accessing business loans I made a final check with BT as many cabs surrounding mine (urban area, seaside town) were having work done but nothing on mine. They told me it was now off the list - same copy and paste reason "commercial viability". Discussions with BT managers ensued, they told me to access CDS (BDUK), they told me that subject to their survey process etc etc I could hold out hope for their programme of infill to get FTTC on my cabinet. I hold off on the expansion and start to miss out on work as I can't shift the large files fast enough.
No news on infill since the initial CDS comment in March 2013 so I recently spoke to them again and lo and behold the same reply as you, incomprehensible State Aid EU legislation. Lost main contract, gone to a freelancer elsewhere with I assume FTTC/P. I cannot afford bonded lines and the like, nor office premises, satellite not feasible, no cable here.
Bitter? Oh yes. Thanks EU and thanks Devon LG/Central Government/BT for a great stitch-up, what a farce.
If you wish feel free to PM me Iain, maybe we can scratch heads together.
BT ADSL2+, Billion 7800N, online since 1987. Macs since 1979. Dreambox fun. Advanced Radio Amateur Licence and an anorak.