Mucky tiled hearth/mantlepiece - how to clean?

[OnTheBottomWithAWomansWeekly]

I've an open fire with a tiled fireplace - 1970's cream tiles.
Grouting has gone black in places and there are burn marks on some of the tiles that won't come off.
I've tried Cif and lots of elbow grease, scrubbing brush, those yellow sponges with green scourer tops, Brillo pads, even bleach.
Any ideas?

treat yourself to a new one - only joking, this company could help you!

Unfortunately I only want to scrub it, don't have the £££ for a new one!

I think they might have advice on how to clean and care for tiles is what I meant though I must admit I did drool over the designs they do!

Have you tried salt and lemon juice?

Soot is greasy. You'll need a degreaser. If neat Fairy Liquid and elbow grease isn't shifting it, then it's off to a bike or car shop for something stronger.

The Internet also suggests white vinegar or lemon juice.

Don't scour it. You'll damage the glaze. Of course some one else may have damaged the glaze in the past so the dirt is soaked in to the ceramic...

Sorry RRS, I got distracted looking at the lovely fireplaces I can't afford, didn't think of looking further on the site!
Looks like it's out with the salt/lemon juice/vinegar (my sitting room will smell luvly!). I'll see how it goes tonight.
Thanks all!