Anyway, looks like I'll be going to the littlest's birthday gathering without R. The ex is still saying that it's not appropriate and basically it's all about me wanting to 'make a statement about my relationship'. Which is not the case but I'm just going to leave it at that. I've said my piece & he's said his. My sister is allowed to join us, but R is not welcome. Not really sure what the logic is for this, but the main priority is the littlest & I know she'll have a great time.
What I have found through Twitter responses to my post are a number of useful resources for separated parents in similar situations to me, such as relationships-scotland.org.uk, oneplusone.org.uk, splittingup-putkidsfirst.org.uk (where you can create a Parenting Plan online) and theparentconnection.org.uk. Tonnes of articles, videos etc with advice on parenting/relationship issues.
My dad & his wife and my sister are going to be staying with us at various points over my weekend (that's me off work until Monday, part-timer that I am!) so we have a couple of days of family meals, playing in the garden (fingers crossed the sun comes back out!) & movie nights etc to look forward to. I've also scheduled in a few play dates. Lots on to keep us entertained! Roll on the weekend :)