Will CCleaner 35 free disk space wipe make all deleted data unrecoverable or should I just get a new hard drive?

Will the 35 free space wipe make all deleted data completely unrecoverable or would it be better to just buy a new hard drive?

Buy a new one.

Wiping it will make it as hard as humanly possible to recover any data - but not 100% !

Given enough resources, be that time, money, motivation or machine power, data or more accurately bits of data, can be recovered.

As to what can then be gleamed from that data - who can say.

However, hammer, drill press, bucket of salt water, (insert favourite technique here) does guarantee 100% chance of data being recovered (providing it's done with the correct amount of vigour) :)