Whittard do a whole range of flavoured coffee - vanilla, chocolate truffle, Irish Cream and hazlenut to name a few - they do them in instant granules or coffee for coffee makers.
I did use these during abstinance on LL - because I didn't think they would be a problem. They weren't a problem for me and didn't affect ketosis or weightloss. However, use with caution - I liked one of them so much that I drank a bucket of it one day and had a really terrible reaction to the caffiene overload and had to take to my bed for a whole day to get over it. That much caffiene on an empty stomach has some very unpleasant side effects I can tell you!
But listen to the wise Mike - if he says no no - then that IS a NO NO.
I just never thought to check - whoops
Laura