I just joined the Glasgow West End one a week ago, and because DL is considerably more expensive than other gyms I had to think long and hard about joining and decided to do my research by looking at websites like this. I agree with other posters that the 3 month notice period isn't made that clear by the membership staff who appear to be on commission and desperate to make a sale.
That said, I'm very glad I joined, it's an excellent facility and it is totally geared towards people like me with kids which is why I joined. We're really enjoying our membership so far!
Top tip: if you pay your membership up front for the year it works out considerably cheaper, for one adult and one child I've saved around £300 by paying up front than if I'd paid by DD.