[bobpark]

I use the Allotment's Pear & Walnut chutney recipe which provides about 6 jars.
I wish to save time by making twice as much. Is it just a case of doubling up on all the ingredients?

[New shoot]

Yes, but obviously there will be a lot more in the pan, so it may take a little longer to reduce to the consistency you want.

Link to the recipe 

http://www.allotment-garden.org/recipe/1892/pear-walnut-chutney-recipe/

[Mrs Bee]

If you double your recipe, you will have to cook it for much longer to get the required consistency which also means that the resulting chutney will be soft and mushy with very little texture. They flavour will not be as good either.

If you are going down the doubling route, don't put all the vegetables and fruit in at the same time keep some back to put in once you have reduced the contents of your pan by a good half.

Also I have found that rather than simmer for hours, it gives a better texture and flavour if you cook it down faster.  Although you do have to keep stirring it to make sure it does not burn.

[New shoot]

If you are going down the doubling route, don't put all the vegetables and fruit in at the same time keep some back to put in once you have reduced the contents of your pan by a good half.

That wouldn't quite work the same way with the recipe the OP is using.  Its also only a 4lb recipe.  I've doubled recipes for similar amounts before and its been fine