Me, the wife and our 2 kids use David Lloyd. For us it's a lifestyle thing as I'm up there around 5 days a week and they use it 3 times a week. We only pay around £140 a month for all 4 of us, that's for use of everything at any time apart from the tennis courts.
I could not say enough good things about it, as for me it's perfect. But then again I've been working out for over 16 years and I feel great on it and therefor want my kids to be as fit and healthy as they can.
So for all the family to work out, swim in excellent heated indoor and outdoor pools and shower and change in excellent changing rooms, not to mention the social aspect we get out of it, as David Lloyd put on free nights where there's a tribute band or a dance nigh etc, all it costs is £4.66 a day.
I get some friends and family say they'd never spend that much on a gym, but there usually the one's who are overweight don't exercise and think nothing of spending £20-30 on takeaways once or twice a week.
I love a pint but now when I take the family out for a couple of drinks, I don't get much change out of £25! that's just 2 drinks each!. There's over 5 days membership for the family gone in an hour and a half

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So my point really is that if your that way inclined and enjoy exercise and not just do it because you think you have to, then David Lloyd membership is well worth it. If your not really into it then there's no doubt you will not get much value from it.
Also it is true that the prices do keep the chavs out, which can only be a good thing ...
