Looks like a great way to spend £250 and get a framed certificate in return.
If you aim to earn your fees from blue chip clients - don't bother - they will attach no weight to membership, nor to lack of it.
If you aim to earn you living from smaller, engagements with non-blue chip clients, then this is the sort of meaningless qualification that might just hoodwink some of the more gullible ones.
You would be better spending the 250 quid on stamps and sending a "I've gone independent" mailshot to all your previous clients and network.