Question Author
Many thanks all for your suggestions. I lost no time in following your advice legend, using 5litre cans of old white emulsion, diluted. As you point out heathfield, it uses an awful lot of paint through absorption. One coat only so far applied, and the walls still look very grey and rock-like! I reckon it will need 2 further coats as recommended to achieve even a 'half-decent' finish; what do you think about masonry paint? Maybe that might produce a more smooth appearance? I'll swear my Mercedes Cabriolet thinks it's in danger of being surrounded by a shabby image!