Didn't intend to post again, but I felt as though I owed it to anyone who stumbles on the blog with the same problems. I can see from my web stats a lot of people have googled the injury symtoms and found their way here.
I went to Cardiff, to see Mr Woodward, a surgeon at the Bupa Hospital and after reading my case history and asking a few questions, he said it sounded like a typical case.
He did a quick exam, pressing each side of my groin, as I twisted to each side and coughed. Straight away he could very clearly feel "a gap" on the right side. My conjoint Tendon should be attached to the inguinal ligament. Mine isn't anymore, it's torn off. Only surgery can fix it. He recommends an open surgery technique, not keyhole. a 6cm slice is made, the tendon reattached, and some semi-disolveable mesh is applied to strengthen the area. The surgery takes about half an hour and he is happy to perform it under a general or a local (nerve block) anaesthetic. He warned that there is always a danger of infection with mesh and sometimes it has to be removed (though it hasn't happened to him yet). He also said that for 1 in 10 the surgery doesn't work, so a 90% success rate if you look at it optimistically. Sometimes he does an adductor tendon release if required, but doesn't think I need it. The cost of the surgery I am waiting for the quote, but I believe it is just over £2000.
So, it was indeed Gilmore's Groin (also referred to as other names as well, groin disruption, sportsmans hernia etc). See the link for a description, which fits like a glove for my symptoms.
I'm going to get it done on 4th November I think, and worry about the cost when MasterCard send me the bill. Recovery time is 4-6 weeks if the operation is a success. I hope to rehab and make a return to running, but there are a lot of possible outcomes (I'm the 1 in 10 who is doesn't work for, or there are other things wrong as well that I find later). For now, I'll live in hope. Thank you for all the comments, I wish you all the best too. Again, thanks to Alex who gave me the surgeon's name. Six months Injured and the surgeon pinpointed the injury in 30 seconds.