Actually, seeing the belly at all suggests it's not a lizard -- legged lizards are extremely quick (the average time I keep them in sight is about 0.4 sec, give or take). I wouldn't get much chance to notice any belly spots even if they had any. On the other hand, newts sit and wait for you to wander over and pick them up.
And I'm sure, NC68, that your description was perfect in every way...
Have a look at
http://www.uksafari.com/wildfiles.htm. Click on Amphibians, then Newt - Smooth, or on Reptiles, Common Lizard. (be careful with newt pictures though, as most photos show them in breeding condition with their fins on -- like the palmate and great crested newts on that page).