Not disconnecting the battery should not make a difference. The only issue you could have with the ABS is if you let the master cylinder run dry to the point where air could have entered the ABS unit, then you may need to cycle the pump to help to move air out. If you did not have air enter the system you should be able to easily bleed the brake system. On a vehicle of that age I would suggest not using the brake pedal to pump the fluid through the system. The master cylinder can build up a ridge in its wear area that can damage the piston seals if the pedal is pushed beyond the its normal area of travel. This can lead to a difficult to diagnose soft pedal feel or pedal that "bleeds down" when holding pressure. The best way would be to pressure bleed the system from the reservoir down. If you do not have access to a pressure bleeder inexpensive vacuum pumps will often come with a fluid container that allows your to pull fluid through the system, both of these will allow you to bleed without moving the master cylinder. As always start at the wheel farthest from the master cylinder and move around the car towards the wheel closest to the master cylinder.
Thanks Francis. The master cylinder has always been full so no air has entered there. I was a bit worried that I had stuffed up but will bleed as normal. I have made up a crude (but it works) pressure bleeder.