So the convenient checkmytrip and classic checkmytrip URLs seem to have gone in 2017.
Last year you could retrieve your PNR like this:
Code:
https://classic.checkmytrip.com/plnext/XCMTXITN/RetrievePNR.action?DIRECT_RETRIEVE=TRUE&REC_LOC=ABCDEF&DIRECT_RETRIEVE_LASTNAME=Smith&SITE=XCMTXITN&LANGUAGE=GB
And you'd get all the relevant information including seating, receipt etc.
Now you get nothing, just a worthless home page for checkmytrip.
Let's hope it's a temporary glitch rather than an Enhancement.