Power Flush or Not?

I need to have a new boiler installed.
Can I get away with not going to the expence of having a power flush before it is installed? The rads are about 25 years old and the old boiler was about 10 years old, the water jacket split.
It is 8mm microbore pipe and the downstairs pipes go under a concrete screeded floor that was done sometime after the pipes were layed.
I had one plumber around when I had a problem with a couple of rads cold, he said because the microbore went under the concrete he would not recomend powerflush incase it caused pin hole leaks in the pipes under the floor. I had another plumber in to quote for a new boiler and he said a power flush would be good for the system, mind you this plumber seems to look at nothing and made his quote out of thin air.
I would like to not go to the expence of the powerflush if I don't have to.

What's the old boiler, and what's the new one?

And have you have any history of corrosion in the system?

Hi,
The old boiler was Bosch worchester danesmore Oil and changing it for probabaly Graunt Vortex 26/32 condensing oil
Yes there has been corrosion before my time, I did run sludge remover in the system for 4 weeks about a 6 weeks before I had problem with Boiler, not much sludge came out.

Microbore pipework is nearly impossible to Powerflush and the radiator ages might prove a problem, the thing to consider is that a flushing machine works on high flow rate and not high presure. I have successfully cleaned microbore pipes with 'Hyperflush' which is a not very aggressive chemical but it has meant removing all the Microbore connected rads and doing them seperately. I would recommend the process but make sure that your installer knows what chemicals to use. Most manufacturers now expect you to clean the system but that doesn't mean that you have to pay for a Powerflush and what is more important make sure that the system is chemically inhibited after the installation.