Bricking up a window- double block construction

[DeeEyeAye]

OK this is more of a brickie question than a window one, but hey.
I have a very small window that needs to go, due to an internal layout change. I've removed the old wooden window frame and now it's time to brick up. The house is made from two leaves of concrete blocks with a cavity (which has been filled with blown insulation at a later date). The outside finish of the house is harling which is painted white.

1. Is it OK to cut blocks to fit the hole, or should I be removing half blocks at the edges?
2. The old concrete windowsill is still in place. Obviously I cannot lay blocks straight onto it because it is sloping. It also sticks out a few inches from the wall. So I guess I need to remove it completely- or can I take an angle grinder to it and cut it back? Bearing in mind everything will eventually be hidden by harling anyway.

Ta for any thoughts on this.

 

[DHFrames]

I'd use furfix to strengthen on the internal and external skin, no need to key the blocks in. In regards to the sill, either take out or just take out the front leaving enough room for your scratch and finish coats

 

[DeeEyeAye]

Thanks, that's encouraging. I'll try taking out the front of the sill with a grinder. I was a bit worried it might have reinforcing in it but I guess that would only apply to a lintel?