I don't know this type but it will depend strongly on the condition. A 1960 plane will be a black hole for airframe parts, due to (a) wear and (b) corrosion. But it may not be, if it has a long history of having been well looked after and hangared. You need a specialist to check it out.
2. What are the cheapest planes you can buy with the lowest running costs? (Any particular ones?)
Among certified ones built from aluminium, I doubt there is much difference, and on something this old, what differences there are will be swamped by the general maintenance. On a pure running cost basis something small and homebuilt will be cheapest to run but you cannot fly it IFR or unrestricted abroad.
3. If following the route PPL -> CPL -> ATPL etc. could you make a career out of flying by starting with a small plane, work up your hours, gradually get bigger then end up flying private jets or cargo planes or something? Or is this 'route' only intended for hobby flying? Any more info relating to this as i'm sure i've got something wrong would be great
I doubt the business opportunity exists in Europe. Any commercial work is so heavily loaded with regulatory garbage (AOC etc) that making a living as a one man band is tough. If you want to build hours to become a commercial pilot then having your own plane will be a great way to do it, and you can go to interesting places while at it. But getting some money for it will be tough.
4. Can you fly in europe (outside UK) with a CPL? What about flying outside Europe?
If country of license issue matches country of aircraft registry, then you have worldwide privileges, noncommercial, VFR. If on that license you also have an IR, then you can fly IFR. But commercial privileges are a different thing and are subject to various national protectionist deals.
About the only context where a CPL alone is good is where you are a paid pilot for an aircraft owner. Then your CPL/IR is good worldwide and no AOC is required.
BTW, the plane you are looking at is N-reg which cannot be taken outside the UK unless you have an
FAA license (reference: FAR 61.3). This is not a huge deal but is probably a level of hassle not warranted at this low level of expenditure.