I have a MK2 escort 1100 (and Cortina GT 1600 hubs and axle) that I'm intending to use as a donor for my first build.
Can anyone please tel me what gearbox is fitted in it and could i bolt it up to a more powerful engine?

Yes you can bolt an1100 gearbox to a more powerful engine.How long it will last is an entirely different matter.

The gearbox you should have is known as the Type 2 with integral bellhousing

It was used on most MK1/MK2 Escorts except the RS and Mexico versions

It was used in the 1600 Mk2 and many Caterham 4 speed gearboxes are also Ford Type 2

You may find that the gear leaver does not run far back enough the transmission tunnel for comfort, you may need to make up an extension or have one of those curved leavers.I used to use the 1100 g'box on a 1600xlow with no probs but to make a neater job I used the 2000E box with a slightly longer tailend because of gear lever position issues.