Channai Dosa is not bad. It close to an authentic Southern Indian cooking but, of course they have to adjust (just like most ethnic restaurants) to cater for the Brits. It's inexpensive, their buffet. Good for the buck but, cash only. Don't come too late, if you want a good selections and freshness - it can get busy and a bit crowded, too. Services are not upto par but, good inexpensive food makes up for it. I would still go back there, when ever I'm in Wembly to watch football.
Better Indian restaurants of course are in London. And you know it gets to be pricey but, you get a nice atmosphere, great services, and good food. I would recommend, Masala Zone (not a buffet, though). They have I think, 7 locations. Not too expensive. Favourite place of my cousin who resides in Thames.
I do enjoy buffets, as well as mid range restaurants, and when I can those fine dining ones (usually on certain occassions).