Don't let the presence of a center tap stop you from using an otherwise suitable transformer. The tap can simply be clipped off close and taped or heat-shink sealed.
Transformers are normally rated in VA which is roughly the AC equivalent of a wattage rating.
You said:
I need a transformer which is capable of transforming 12V into 240V ac.
However the 12V side must be cabable of delivering 10A. Preferably without a centre tap.
That's a little bit confusing -- if the 12V side is the primary, then it won't be "delivering" 10 amps...
As a general rule of thumb, a voltage step-up across a transformer produces a similar step-down in current, and vice-versa. If you need to raise 12VAC to 240VAC, you need a step-up of 20:1 (12 x 20 = 240). If desired current output is 10A, this transformer would need to be able to handle 200A on its primary side! On the other hand, if the 10A is your projected input current, you are only talking about 500mA at the secondaries...
So... where does the 10A requirement come in?
Or... are you trying to drop a 240VAC input to a 10A @ 12VAC output?
Give us a little better info if you want some more help.