A friend (the one who brought me the potatoes), emailed me this, specially adapted for me! Bit long but might be helpful.:
Potatoes
Plant your chitted (yours are already chatted) potatoes when the soil has started to warm up, usually from mid-March or early April. Start by digging a trench 7.5-13cm (3-5in) deep, although the exact depth should vary according to the variety of potato you are planting. You have Sharpe?s Express, 5in deep.
Plant early (yours are earlies) potatoes about 30cm (12in) apart with 40-50cm (16-20in) between the rows. Handle your chitted tubers with care, gently setting them into the trench with the shoots pointing upwards, being careful not to break the shoots. Cover the potatoes lightly with soil. As soon as the shoots appear, earth up each plant by covering it with a pile of soil (like a growing sandcastle) so that the shoots are just buried. You need to do this at regular intervals and by the end of the season each plant will have a small mound around it about 15cm (6in) high.
How to harvest
Your home-grown potatoes should be ready for lifting from June, depending on the growing conditions. Earlies can be lifted and eaten as soon as they are ready. This will be when above-ground growth is still green, and usually as soon as the flowers open, although some varieties do not flower. I?ll tell you about when.
Growing tips
Potatoes like plenty of sun, so avoid planting them in frost-prone sites, as these conditions can damage the developing foliage. If you're starting up a vegetable plot on very weedy ground or old grassland, potatoes may help swamp out weeds with their fast-growing, extensive foliage.
It is particularly important that there is adequate water once the tubers have reached the size of marbles. Unless there is regular, ample rainfall, the size and quality of the crop will be reduced if you don't water your potatoes.
Hope this is helpful.