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Some groups are more formal and work very hard at building business referrals. They are also more structured: for example, you join one group, weekly attendance is expected as well as weekly contributions in some way. BNI is a very good example of this: http://www.bni.com/
My group meets every Friday (Trafford Park) at 7am
Lesss formal, you can join 4Networking (the organisation rather than one group), which has meetings across the North West on most days of the week. You can attend as many (or as few) meetings as you like, whenever and wherever you like.
My groups meet every other Tuesday (Trafford Park) and Thursday (Swinton)
Let me know if you want to come and I'll get you an invitation.