Friends

Any advice please! I am a South London mum to an 18 month old toddler, and am getting frustrated with making friends with other mums. Friends have always been massively important to me, as I have a small family, and my dad died when I was little. I admit that I'm quite a hyper person, always on the go, and maybe a bit intense at times, but I've always found it reasonably easy to meet people and have a laugh doing things together, often through sport (tennis, walking, climbing, cycling, swimming).
My two oldest friends live outside London and became mums at the same time as me, 18 months ago. They are both now really busy with difficulties at work, moving house, and one of them is starting a business. I therefore don't get to speak to them much or see them more than every few months if I'm lucky. I am lucky that I don't have any of these stresses, but I have considerably less family support.
Since becoming a mum I have made massive efforts to meet other mums and organise interesting things to do, e.g. baby massage, baby swimming, badminton, picnics. I did the NCT thing but everyone seemed very tired for the first few months and we drifted apart. Through another postnatal group, I have met some sweet ladies and gorgeous kids, but I remain the one who organises everything. Plus, I have introduced them to other friends and also to my family and husband, but everyone else seems to want to keep this mums' circle separate from family and other friends.
I love being a mum but really miss my old friends, their generosity and humour and sheer fizz. I have tried to look at sports for mother and toddler but have not found much apart from babyswimming, which I have already tried for a long time. Will I ever meet any proper mum friends and can anyone suggest ways of doing this?