I get 10 000£ per year or 820 £ a month. Between 8 000 and 12 ooo £ per year is normal. What makes you think you can negotiate your stipend? It is normaly a fixed rate by the funding organisation - take it or leave it.
Yepp,
but you either decide according to who pays more or which lab has a better reputation or the project that interests you more. You won't get rich during your PhD. Its take it or leave it. If you want those 40% more then go for a 12 000 stipend.
You won't be able to negotiate your grant. If you don't think it's enough you'll have to turn it down flat and look for a PhD with a better studentship. CAST and CASE awards usually pay the most.