* FTSE 100 up 0.9 percent

* Marks & Spencer, Next gains on firm results * Banks, miners reclaim ground

By Simon Falush

LONDON, Nov 4 (Reuters) - Britain's top share index gained 0.9 percent early on Wednesday as commodity stocks and banks recovered some ground lost the previous session and with retailers led higher by Marks & Spencer (MKS.L: Quote, Profile, Research) after firm results.

By 0855 GMT the FTSE 100 .FTSE was up 42.59 points at 5,079.80 having closed 1.3 percent weaker on Tuesday dented by a sharp sell-off in banks after a shake-up at part-nationalised Royal Bank of Scotland and Lloyds Banking Group (LLOY.L: Quote, Profile, Research).

After the sharp retreat on Tuesday, banks gave a big lift to the index Wednesday, with investors re-evaluating the climate for the sector following the 31 billion pounds ($51.1 billion) in funding from the government agreed for Lloyds and RBS.

Royal Bank of Scotland (RBS.L: Quote, Profile, Research) and Lloyds Banking Group (LLOY.L: Quote, Profile, Research) added 3 and 2.1 percent respectively, while Barclays (BARC.L: Quote, Profile, Research), HSBC (HSBA.L: Quote, Profile, Research), Standard Chartered (STAN.L: Quote, Profile, Research) gained 1.1 to 2.6 percent.

Elsewhere among financials, insurer Aviva (AV.L: Quote, Profile, Research) was up 4.7 percent shrugging aside results that were slightly below forecast, as investors reacted positively to its solvency position.