I can't help you with a service, unfortunately. Bunnings do have a tile cutter for sale at the moment for $22 and will do up to a 400mm tile. My tiles for the ensuite were 450mm so I ended up cutting them with a 4 inch diameter diamond cutting disc attached to my circular saw. It was like cutting butter with a hot knife. The diamond blade was $14 from a tile supplier.
Actually why not take the tiles to the place you bought them with 6 icy cold brown bottles of liquid currency and ask nicely if they could cut along the lines you have drawn in pencil.
cheers,