shock mounting bolts for Boardman 650b

[MADB]

I got this secondhand knowing that it needed some TLC,anyway the first thing I need to sort out is some now rear shock mounting bolts as the one on the bike are rusty as hell, Halfords are being very helpful at not having a clue. So does any one know if these are a normal bolt I could find in a good bolt shop? I have never taken anything like this apart so it all new to me.

Any help tips where to go what to look for would help.

Thanks