Jim, thanks for the tip. I like bananas
As I said the condition has only recently been diagnosed and it will be monitored over the next few months or more to see if it improves and if not how it can be brought under control. One thing I have found over the past two months is that I like oats which is probably just as well. 
As for the experience of the walk I accept that mistakes were made. My friend Dave who has an ice axe and knows how to use it didn't take it on the walk. As he said afterwards, if he'd taken it he could have cut footsteps across the snow fields and made things so much easier for both of us. My main mistake was letting us push on for so long without a rest to restore energy and consider our position. I also feel I deferred a little too much to my partner and I had to argue my case to give up and turn back. That can be a difficult one, arguing one's postion with someone who has more experience than you and who you're inclined to respect and therefore follow.
With regards to OPs obviously greater experience all I can say is that I don't see the point in learning how to use an ice axe for a once in a lifetime experience. My friend Dave has an ice axe but he's not used it in perhaps 15+ years. We don't normally get into the kind of conditions that warrant it and have no intention of doing so. But we still had microspikes and were most impressed at the grip and traction they provided on the ascent of Skiddaw. We had hoped to get up on to Helvellyn. We didn't because the first day's walk took too much out of us and we weren't fit enough. Even if we'd tried we'd have tried an ascent from the Thirlmere side of the mountain, possibly via Sticks Pass and the long climb up along the ridge. There's no way I'd ever do Striding or Swirral edges under snow. Perhaps OP would say given the conditions up there we'd be unwise to try even an easy route but the photos put up on the LakeDistrict weatherline website make it so attractive.
But this is getting off topic and becoming something of an uncomfortable exmination and rehash of what went wrong that day. We know most of what went wrong. Being a little stubborn we might go back and do the route again under MUCH better conditions with more daylight hours so we can take our time over the climb.
I'd still like to thank all those who have posted ideas for what to take in the way of food and for a generally encouraging and positive response.