@headoutofthesand
I realise I made some poor decisions of Wednesday, mainly due to ignorance (grapes) and forgetfulness (sweetcorn)
This is why it's important to read the resources on the spreadsheet. Look at the veg carb counter - perhaps print it out? - and make sure you know which are the lower carb veg
What worries me more is, for example, having tuna mayo and thinking that it is fine but, unless I have made it, not knowing how low carb the mayo is. But then I wouldn't be able to actually measure my carbs anyway as I don't know what is in it or how much I have had.
Most mayo is relatively low carb - but they will all show the carb count on the back of the bottle/jar! Why not try measuring out a tablespoon (25ml) to get a feel for how much that is, so you'll know how many carbs are in your brand of mayo?
Carb counts for mayo vary hugely, so check them out when you're shopping. From memory, I think Delouis is the lowest, but this brand isn't available everywhere, and it is pretty expensive though.
I suppose I could take lunch to work and control it that way but everyone eats together (it's free) and considered by the management to be an important aspect of the company so it would be odd not to go
Well, just because it's expected doesn't mean that you have to do this. And even if you do, there must be some low carb options? If they don't (or won't - you could always ask the caterers!) provide anything that's low carb, then that's your argument for bringing in your own food.
One of the things that is really difficult about low carbing is the fact that the world isn't made for it. And so this does mean that you have to plan, plan and plan again.