I totally agree with Erik.

The ARM core is embedded in thousands of products (including most mobile phones), and is now becoming widely available as a microcontroller component - and ARM's recent bid for Triscend (although unsuccessful) indicates that ARM are keen to grow this!
There is therefore a vast amount of support, tools and experience available.
Even Keil now supports ARM (currently using the GNU tools, but their own are due out soon).

And it's British!
ARM is a 32-bit processor, but don't let that worry you for memory requirements - the ARM instruction set can work in "Thumb" mode, requiring only 16-bit wide memory.

I suppose I should add that I have no affiliation with ARM.