The Sudoku grid is a 9km x 9km square centred on Northwich. Each 1km x 1km Ordnance Survey grid square in this area represents a cell in the Sudoku puzzle. The SW corner of the grid is at N053°12.998', W002°35.127' (SJ6100069000); the NE corner of the grid is at N053°17.885', W002°27.096' (SJ7000078000).

Image produced from the Ordnance Survey Get-a-map service.Image reproduced with kind permission of Ordnance Survey and Ordnance Survey of Northern Ireland.
Hidden in 23 of those squares are individual Geocaches. Each of these contains a number that you need to solve the puzzle. The information in the container tells you whereabouts in the puzzle the number should go.
The table below shows which caches you need to find.
Now the difficult bit. You will have noticed that not all the cells that are marked above have a cache associated with them. There are 4 cells that have no hint. You will have to use your skill and judgement to work out what these missing numbers are. Everything you need to do that is on this page.
Here's a blank Sudoku grid that you can fill in as you find the clues
Once you have solved the puzzle, use the formula below to work out the coordinates of the cache. It is hidden somewhere within the 81 square km Sudoku grid. The cache is an ammo box with the usual log book and swaps. For the first to find,there is also an unregistered OCB geocoin and a customised "Northwich Sudoku" first to find badge.
There is space for two cars to park at N0(d1)(e2)°(e4)(h7).(f5)(h2)(e7)', W 00(f1)°(h4)0.(h8)(a5)(d2)'
The cache is hidden at:
N 0(d1)(e2)°(e4)(a2).(c8)(b9)(d4)', W 00(f1)°(b6)(g8).(b7)(h4)(f3)'
You can check your answers for this puzzle on Geochecker.com.