You probably require a 3W bulb.
3W GU10 low energy bulbs emit as much light energy as a conventional 35W GU10 bulb. At first glance that figure might seem a bit high for your needs but, because the spectral qualities of the light from low energy bulbs are different from those of conventional bulbs, many people seem to find that low energy bulbs don't actually appear as bright as their 'equivalent wattage' suggests.
However Philips 'Econic' range (which they quote as lasting 15 years, based on 1000 hours use per year) don't come cheap:
http://www.johnlewis....uct.aspx?source=14798
(That's a 'bargain', by the way. They're £5 dearer on the official Philips website!)
Philips also produce a far cheaper range of low energy bulbs, where a 7W bulb is nominally rated as equivalent to 25W but they're only expected to last for 8 years (based upon 1000 hours use per year):
http://www.johnlewis....30439663/Product.aspx
Chris