new spade

I find spades a bit of a personal thing, I would suggest you pop along to a few shops and try them, not digging of course but to feel the weight, height even the way the handle feels etc, I have four spades, three of which I hate to use.
I generally prefer the stainless types as the surface of the spade is very smooth and will cut through soil better that the painted ones.
Hope this helps

There are 2 types of spade used regularly a heavy spade for hard digging and what I would say is a cutting spade.

The 1st spade (Spear and Jackson or Bulldog £27) would be for heavy work tough soils and clay with the odd stone needing prised out. 

2nd spade same makes (£17) edging grass planting shrubs and light digging in farly loose soils or manure, a good bit lighter in manufacture espically the spade metal.

I personally own the 1st spade as I would be a bit hard on the spade with work and it lasts me a bit longer without breaking the shaft or bending the spade.


Busy Bee

I'm the same height as you and I have stuck with a border fork and spade.  They have smaller heads, but that means you're not trying to move too much soil in one go.  Definitely go and try a few out - some have really nasty edges / burrs on the plastic handles.

Mine are Wilkinson Sword s/steel and they've done pretty well so far.