Thanks Richard for your help!
I plucked up the courage to start machining some of my castings this evening. I seemed to have some sort of unfounded fear that I`d manage to chip or crack a casting some how, but strangely enough, it all went very well....infact, too well !
Despite reading all the books and the current ME article running at present on the 10V build, I chose to use my mill to true up the castings rather than mess around with jigs on the lathe. I`m not trying to be lazy but most of the books are aimed at lathe only workshops so I may as well utilise what I have. It was an excellent opportunity to use my X-axis controller power feed for the first time and I`m buzzing, it worked an absolute blinder! The finish is top notch and ten times better than what I was getting by hand and also the ease of use was great - find your left and right limits and just keep working between them taking cuts each time! It was luxury!!
Less woffle...here are some pictures, they are self explanatory:
Truing up the machine base and top.

I was impressed with the finish using my power feed!

Box bed top and bottom

Feet of the standard

Standard top which will seat the cylinder "before"!

,...and after

And all the bits piled in position!

Machining the holes/slots for the fly wheel bushes - I was wanting to use an end mill but didn`t have one of the right size so a drill bit did the job just as well. I took it through nice and slowly.

And how the bearing fits in position

Ok, nothing amazing....I best get reading, onto the more taxing jobs now!!