Smaller spare bedroom

Personally I think it is easiest when you choose a palate of colours that work with each other. To make this work choose three neutrals to start with. Given how this house was previously decorated it suggests Mum prefers warmer colours. So say you like Dulux paint you look at their site and choose a soft white such as white cotton and a warm neutral such as Egyptian cotton and then another such as Jurassic Stone. Then I would use these as a starting point and use them again and again in different rooms adding accents.
So for instance in the lounge you might paint the woodwork and coving in White cotton, the walls and ceiling in Egyptian Cotton and then a punch of colour in one wall such as the chimney breast. In the hallway you might use White Cotton and Jurassic Stone (in small spaces it is sometimes better to have a simpler palate to make it feel less cluttered and bigger.)
In a bedroom you could paint walls and woodwork in White cotton but paint a wall for contrast.
Then I would be thinking about what accent colour to continue throughout- So if Mum likes green the living room accent wall could be a bold colour like Heathland, but you might choose a more restful green in the bedroom such as Crushed Aloe, and something fresher for the Kitchen such as Spring meadow. I would use the same neutrals again and again and paint colour with restraint. Then of course you layer on more colour with soft furnishings and you might also give furniture a fresh lease of life by painting it - this trick also helps tie picture frames into a scheme.

I have finally got her to choose the main colour, she has gone for greys as the main with accent colours to go in the rooms, the kitchen has just been completed with a cream shaker kitchen and light green walls.
The living room has got dark green sofas (I can see a pattern starting) This end of the house is different to the rest of the house as it has wooden beams and a wood burner set into a brick fire place and lower ceilings

Have you considered choosing a grey carpet? Easy
on the eye, they make a great base shade for room and suit both period and
contemporary decorating schemes. It looks sophisticated in living rooms, it
makes bedrooms feel soothing and creates a welcoming space in entrances. The simplicity of a grey floor makes it a very practical investment for any room in the home also, Cormar offers a range of grey toned flooring options to suit a range of budgets. http://www.cormarcarpets.co.uk/carpet-ranges.php