Rear derailleur shifting from 1st to 7/8th with one click I have recently replaced shifter cable and reset the pulleys so that they are in line with the cogs.  I've set the high and low limits and have the gears shifting nicely upward &amp; have fine tuned with the barrel adjuster.  When shifting back down the gears just jump from 1st almost straight down to 7 &amp; 8th cog after only just one click of the shifter!!

Help....any recommendations on how to fix please?  Cheers
My first thought is you need to clean your shifter. There is a ratcheting mechanism in there which is the thing that makes the distinct clicks when you shift. When the grease is old the little pawl (the thing that locks into the teeth of the ratchet wheel)  will sometimes not want to rotate properly which can cause your shifter to skip gears. 
Removing the shifter cover, spraying it with plenty of wd-40 or a similar product and shifting up and down a bunch of times should solve the problem in most cases. If that doesn't help you might have to clean it a bit better using for example cotton buds and a solvent or cotton buds sprayed with wd-40.

This phenomenon is called a 'sticky shifter' iirc. Here is a video on how to possibly solve it: 

                
            
(Note: the issue shown in the video is not your exact issue but the video does show how the ratcheting mechanism works and following the steps in the video should probably solve your issue as well