For the UK and a G-reg aircraft in VMC, I believe the legal minimum is that the safety pilot holds a PPL, i.e. that they are capable of acting as P1 should the need arise. That said, some clubs (including the one I fly with most regularly) and/or insurance companies may impose a tighter restriction - even for simulated IFR flight in VMC using foggles or similar the safety pilot must hold at least a PPL/IMC, for example. Always check the flying orders book - all good clubs should have one, although that might not apply to privately owned aircraft.
Sennadog - flying from the right-hand seat is not a lot different from flying from the left in my experience, although I haven't tried take-offs or landings from the right yet. I've also not found much difficulty going from stick to yoke. Don't forget that most single-seat or tandem-seat planes actually look like the right-hand side of most training aircraft, i.e. the stick is in the right-hand and the throttle in the left hand. Having said all that, I'm sure that any transition between types is made easier or more difficult depending on the skills (or in my case lack thereof) of the pilot - certainly my worst ever landing (including those during PPL training) occurred on my first flight in a new type where I had considerable experience on the smaller version of the same aircraft - thank God the instructor was ready for my faux-pas!
Cheers,
MD.