Hello again. There have been some developments since my last post and for those of you who would like to see, here it is...
www.mumsnet.com/Talk/relationships/2639745-Am-I-being-used?watched=1&msgid=61128661#61128661
To summarise, my partner and I are planning to take a friend for a trip to London when she visits from overseas soon. He mentioned at some point that we could save money with a group ticket and I said something along the lines of "Sounds good but I may be in London at that time anyway." He posted in a group chat what this would cost between us and I confirmed with him later that I would in fact be in London anyway so could not be part of the group ticket to which he replied "you can buy us lunch then". I took this as a joke but he stated that this was only fair since they would now be paying £30 more.
As a compromise I offered to look for cheap tickets for the both of them and book them by means of an apology just to avaoid an argument. Upon researching I found out that the extra cost to them would be no more than £8 each. I'm willing to admit that this could have been an innocent mistake on his part and so informed him of this in as friendly a manner as I could while also pointing out it would have been nice if he'd confirmed if I was in London or not at before messaging us all. I have also offered to still book the ticket so he doesn't have to stress.
He hasn't replied yet but honestly I'm terrified because I know I will wake up to an angry message telling me I'd agreed to the idea (I'm almost certain I didn't) and he'll call me disrespectful or say something horrible.
I just need some advice on how to respond to keep things calm for the moment so there are no tensions during our trip. I can deal with the relationship as a whole afterwards.
A huge thanks to those who responded to my last post and a huge thank you to the forum in general.