Mike right about train prices but Scotrail isnt very organised /cancellations/delays aplenty. Also avoid the trains if theres an "old firm" match on as it can be be very intimidating.

Bannockburn is right next to Stirling so you can combine it with Stirling castle/Wallace monument.

Like I say if you want to see Ireland then book a seperate trip to Ireland and allow a week at least, Ulster isnt the nicest place, you really want to keep to the south.

There is a firm called lochs and glens http://www.lochsandglens.com/

these guys are pretty good if a little on the dear side.

Again Mike pointed out the price of petrol, its staggeringly expensive compared to other countries.

do your homework and plan correctly and youll have a great time