Thank you for the ideas, sorry late reply, everything is slowly going nowhere.
Short answer I'm going to write a grovelling message to openreach and see if they can just let her continue on adsl for a while. Otherwise will look into the very helpful links above on ECC exceptions.
Longer answer,
Drive is about 400m up a hill from main road and goes under main railway line.
http://oakhouse.byethost32.com/fibre/fibre1.jpg
http://oakhouse.byethost32.com/fibre/fibre2.jpg
If curious you can see above where the line goes along poles under the railway line. Having extracted a powerpoint from zen it does indeed appear they wish to bury a duct between the two poles through the tunnel. Possibly solid rock ground there. Why they can't leave it on poles who knows. That and cutting back seven trees is the main costs. Quote below which doesn't make sense to me, how that translates to us paying £1500 as contributing half?
What a mess, reading up on ECC charges they are indeed in the terms and conditions though most people say they apply where a line is additional or where they wouldn't commercially chose to put one. Which if its the customers only option on an existing line you would think they would be obliged to do it to continue some sort of universal service obligation, but perhaps not. Tried communicating with BT and asking if they were more generous in costs but they just insisted, "special offer no install costs" and when I pushed about ECC charges they just dodged confusedly and then ended chat or hung up.
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ECC Chargeable Items:
Survey x 1= 0
Softway duct x 53M = 1585.76 (CP)
Tree Cutting X 7Span = 604.41 (OP)
Total Cost: 2190.17
Split Cost = (NO)
Total Cost to Openreach =604.41
Total Cost to CP = 1585.76
Build Days = 115
Job Description: 53M Softway duct and 7span tree cutting required.