I'm not from the UK but I'm having a bit of a problem renewing right now because they want the CBC and the diploma apostilled, so I'm working on getting those right now. the transcripts come sealed. And they were returned to me still sealed. I didn't need to get them apostilled.
I was given a year to get it all done, but another immigrations officer told me I didn't need them; that was based on some faulty information that I gave him. My coteacher was on maternity leave, so I didn't discover my mistake until she returned. So now I have about 10 weeks to complete the clearance and I'm told it might take 4 weeks or as much as 16 weeks. I was told if I had them apostiled to begin, I might not be having this problem right now. I may have to leave the country until I have the CBC, so I suggest you bite the bullet and do whatever you have to. Its a lot more expensive to raise the airplane money to take care of business, then it is to just do it right the first time. maybe you can learn from my mistakes?