I run a business on excel sheets too, have done so for over 10 years.
I have tried accounting software but it just does my head in. A spreadsheet is just like a good old cashbook, except that it adds up the sums for you automatically.
It was my accountant who actually recommended I just use excel (he does my year-end accounts off that, I do the monthly book keeping, and my own VAT returns)
My set up looks like this:
Two tabs/pages, ins and outs.
I download bank statements onto excel, and use that as the basis (the 'gross' column) on both pages (separate out credits & debits with simple sorting)
On each page I have a separate column for any cash transactions, and a separate column for VAT.
Then I run more columns off to the right with different cost (or income) categories (e.g. fuel, feed, vet fees, etc) where I repeat amounts from the main columns just so that I can get a breakdown of all the different types of expense. Those side columns are net, i.e. I take off the VAT and put that in the VAT column.
There is a totals line at the bottom, that in each column reconciles the bank statement, the cash box, the VAT received or payable, and totals for the various cost or income posts.
I have some simple formulas at the bottom (i.e. tell excel with boxes from both pages to add up) to get me the figures I need to put in the VAT return.
It really is very simple but it works.
(perhaps it doesn't sound so simple if 'narrated' as above - happy to send a template by pm if anyone is interested)