Sorry Scruffyhound I missed your last reply! Yes, you certainly do get told a different thing every time, it is just down to luck who you get
and it is grossly unfair. Most people are just trying to do the right thing and don't realise how insanely complicated the system is.
Anyway, I am updating with GOOD NEWS!! This won't apply to you unfortunately but maybe for anyone else reading now or in the future it may help.
Basically it dawned on me that maybe I could change the date of my self employment and move it back, as I only started my self-employment in June i.e. within the 66 week test period. So I rang up the self-employment helpline and asked.. and they said, yep, no problem, but you will have to pay NICs (oh noes!!).
So I now officially started my self employment in April.. and guess what, I didn't have that stupid certificate then as it only started in June. So I cheerfully paid my "missing" NICs to bring me up to the required amount for MA, and wrote an appeal letter to Jobcentre Plus.
On the downside the HMRC NIC office wanted paying for all the NICs since April (about £88 or something silly) as my certificate has been "cancelled as if it never existed" (Jobcentre Plus is in two minds as to whether this counts for the purposes of MA or not, it depends entirely on who you speak to so be warned) But £88 is a great investment in return for my otherwise denied £4,000.
So as far as the MA people at Jobcentre Plus are concerned, I now have more than enough NICs paid with no stupid certificate attached. And today I rang them and they confirmed that I get my MA at the highest rate, backdated to 20th February. HALLELUJAH!!
Persistence and a lot of head scratching got me there in the end. To say I am relieved is an understatement.. 
Oh, and in case anyone is interested, apparently it's okay to receive payment for work done before your MA starts during the MA period - I still have several clients who owe me £££.
This has been a very good week! 