It's bonkers that they are not willing to refund (without admin charge for the return) the outbound and return advance tickets that are on the one booking because one half of the ticket falls outwith the affected dates that have currently been communicated.
It's difficult to argue that they are obliged to offer the refund for a return journey if it's beyond the currently expected period of closure. Personally I would because if you can't get there I don't understand how they can expect you to get back again by train.
However, others will disagree, taking a more literal view of the conditions. Were you speaking to Web Support? If so it could be worth trying to get back in touch with Customer Relations, from whom it may be easier to persuade, given the inconvenience and obvious difficulty to you, a goodwill gesture to the value of your unusable ticket by means of an e-voucher if you booked with them (or paper vouchers if not).
My views in general are of mixed disappointment. The charges of fragmentation, inwardness and looking after only one's own are too often levelled at TOCs and rebutted as an acceptable deal for passengers by so many people on here, and yet here we are with them doing very little to make the customer feel better.
It's very simple, you are supposed to be providing a service as one and a huge majority of your customers have no recognition of cross-Company issues. The rail service is either good or its poor. And at the minute, which is it?
Well tha s a start. I do however wonder how many pax are arriving at Crewe just after Midnight having not been able to leave Edinburgh until the regular 18:52 departure time which would normally guarantee arrival at BHM before 11pm and expect to be taxid or hotel'd as a result of the late WCML train terminating there?
The night I got stuck at Carlisle for over an hour because the 1949 to London didn't wait for the Voyagers from Glasgow (I arrived at Carlisle at 1954 and left at 2126) there were some passengers there for London, Nottingham, Walsall, Chester, Stafford and Birkenhead. They arrived shortly after I did by bus from Glasgow, and were all sent to Crewe (arr 2326) for a taxi to their destination!
...
That TPE have asked VTWC for mutual ticket acceptance again, but VTWC have refused.
...
Lots of suggestions that VT (both sides) are not playing fair...
At times it does slightly shock me that management are happy that effectively blame problems on other TOCs to their staff.
Although you'll note that XC were the first to pull the plug.