Hi Norman. Standard autoharp stringing makes the instrument ideal in C and F, good in G, and mostly playable in D and Bb. Hence the lack of a Bm chord. One reason I had Keith Young 3 key diatonic built was so I could play fiddle tunes in D and A.

Although there is some variation, most autoharps are set up in a circle of fifths, left to right. Let's say you're playing in F. The chord to your right is the fifth chord in that key - a C. The chord to the right of that (G) is the fifth chord for the key of C. And so on. So you always have the keys needed for a simple song in any given key close together. For playing in F, your chords are F (fundamental) Bb (fourth) and C (fifth). You'll also have a relative minor of Dm. In Bb, you'll have a similar arrangement - Bb (fundamental), Eb (fourth) and F (fifth), with a relative minor of Gm. By using the Eb when playing in F, you can play more modal tunes. Sticking with F, the Gm and Am are also very useful chords for creating more interesting arrangements.

For tuning with a tuner, I recommend finding an alligator clip - I like the ones by Crate - that you can clip on to a tuning peg and pick up the vibration of the strings. You plug that right into the tuner. I find that as long as it's touching anything metal somewhere on the instrument, it will pick up fairly well. (Though I confess I use a magnetic pickup for tuning on my old 'harp and upgraded to transducer pads on the diatonic - so I use the clips for guitars mostly.)

I've never been to the UK (though I'm always open to invitations), so I can't help you on supplies.

Good luck, and enjoy your 'harp. Keep it tuned, don't be afraid to get creative, and you'll be amazed at what it can do.

Dan