Ok so i finally got round to changing those wall tiles the other day, when i removed cracked tiles there was a hairline crack on the plaster behind, i covered it with homelux matting to try and take the stress and told them to keep an eye on it for future cracks, may have to replace wall at some point, plasterer originally offered to replaster wall for £100 when they removed old tiles but they didnt want to pay the money, am guessing some damage was done then, but it looked ok when i tiled it.