I have a 60 day visa (issued by the thai embassy in the uk) and have just arrived in Bangkok. Can i get my visa extended to 90 days straight away by the immigration office or do i need to wait a certain amount of time?

Thanks in advance

Very unlikely. You will have no problem extending within the last couple of weeks, but any less than that would be at the discretion of the IO.

I have been told when attempting to get that 30 day extension that immigration would like that i do a least the first 30 days iof the original 60 day entry before applying or that 30 day entension.