Thanks Mr_e!

I actually tried 8mhz and 4mhz internal using the following settings:

DEFINE OSC 8
OSCCON=%01110000

DEFINE OSC 4
OSCCON=%01100000

My fuse setting was INTRC. I can't find anything else of relevance to osc speed in fuses. It's not a major problem as ultimately I will use a 20mhz crystal but it would enhance my understanding for future projects to be able to use the internal osc.

Cheers

Rich