Is there any real point in changing my Con rod bolts for ARP bolts at about £60? I've never heard of these breaking and if ford made the st170 stronger and using forged con rods surely they used bolts that would stand up to it.

If you're not increasing the power then there's no need to change them as long as you haven't undone them. However, one has to bear in mind that the reciprocating loads on bolts lead to fatigue, and the manufacturers specify their bolts to certain tolerances. I've never heard of these bolts going, but I increased the BHP spec on my duratec from 130 to 215, and all the bolts are ARP.

Their production and design approaches are second to none and their bolts are so strong, they can be reused in certain circumstances that normally they couldn't. For instance, my cylinder head bolts are going to be replaced with studs, and the studs can be reused. So, when I strip the engine next and add uprated pistons and rods, I'll have saved the cost on the bolts straight away.

If you can afford them, fit them, buy peace of mind.

Con rod bolts are to manufacturers max revs plus a bit
For instance Pinto good to 6800rpm
Zetec red lines at 6500 so should be good to 7000 if you are reving to 7500 or 8000 I would go ARP