OK things didn't quite go to plan, I think I shorted it out somehow.

I have blown the H-Bridge.

Not to worry, ordered another one.

As for the oscillator with the 555 timer, I'm not sure I got 2 waves 180 deg appart. I think all I got was 2 square waves in phase which may have been the problem.

Anyway, I have ordered a 556 which should be capable of producing the 2 waves.

Useful calculators here:

http://pcbheaven.com/drcalculus/index.php?calc=555astable


Or using a 555 timer with an inverting amplifier using a transistor.

Another change I may make is to upgrade the H-Bridge. The SN744681 has a max voltage of 36, I am feeding in 57! The upgrade I have in mind is to one that takes 60V - NJM2670SMD - I've looked on Farnel and can't find it by this name.