Many thanks to you all.
I do tend to use a monopod whenever possible for both my lenses and I purchased a SLIK PRO 700 DX tripod to use in conjuction with the Sigma lens but I have learned another valuable lesson there in that it all weighs a tremendous ammount and is not very portable ! I need some weight training I reckon!!
The Tamron lens performs very well hand held together with its optical stabilisation but I suppose it may be due to the fact that it only goes up to 270mm.
I must run a few tests with the Sigma lens to try and find this 'sweet spot' I read about and I will try firing on the outbreath as you suggest 'Ince'
I will keep you posted on my progress hopefully with all of the advice taken onboard.
Unfortunately I have had to wield a paintbrush rather than the camera this weekend and missed some good weather but hope to photograph some of the migrant birds about to arrive to spend winter with us.