Oxford Blue - you can request your acceptance and certificate be returned to you.
I forget the details but after a month or two of the offer closing they have to return yours if you write to the registrars requesting it on the first day you are entitled to cancel your acceptance.
I have done this in the past including lasy year with Countryside.
There is nothing to gain by accepting this offer. You will only get £2 if it goes ahead and there is £1.9725 available on the open market. I am keeping my cert and so far no follow up mailing to me.
However my opinion is that the price cannot afford to go backwards. If it does I don't believe a higher offer will come at this moment for O2
I hope this helps, the registrars will have to return your certificate in a while if you ask now