Hi Ruth and Charlotte
I've been looking through my copy of the Hackman Transcripts (BTs) for Hannington and think I may have found some helpful information for you

Unfortunately, I couldn't get the marriage you wanted, Ruth, because the period covered is only 1780 to 1812.
I looked for all Instrell or variant entries over the period and found the following baptisms (No marriages or burials for the name)
18 Mar 1781 - David, son of William and Martha Enstral
5 Oct 1783 - Richard, son of William and Martha Instrell
11 May 1788 - William, son of William and Martha Instrel
13 Jul 1794 - Joseph, son of William and Martha Enstral
I couldn't find a Charles Instrell and there were no Diana's of any surname. However, the register for 1795 was marked as missing and of course some children could have been baptised in a neighbouring village (or not at all, if you're really unlucky

)
Someone may be able to check the actual registers if they are going to the Hampshire Record Office in the near future......
By the way - do you have the 1841 census for Joseph and Diana? If not, I'll post it.
Best wishes
Angela