Dear Markieg. I can't help or advise, but I could only sympathise. Been there (haven't) done that (booking I mean).
If united.com sux, UK website is a hoover.
The stupid messages about phone numbers, or lack of thereof are every day occurence. Trying to book on US website without US CC will get you nowhere. You'll get nowhere also by calling US reservations number, because they won't accept payment by non-US CC. Why not calling UK reservations? Well... good luck. First of all it's not really UK but Indian and historical links don't help here at all. Also it's only open till 7:00PM, so not much use for it in the evening. Yes, they will take money off your UK CC, but first they have to understand what do you want and why. If they don't, which is a prevalent tendency, they could always consult with supervisor, which takes hours and keep other callers waiting. Until 7:00PM, when they close and leave you at mercy of UA websites and US reservations. Which of course is as useful as described earlier. There's possibility that you could book with US reservations and request TOD, but you can't choose your seat until ticketed, so when flight is full you'd end in middle seat in last rows of E- even if you're on full economy fare. I know only too well...
Conclusion of my post? I'm optimist. Why? Simple - it cannot get any worse.