with the US commitment in the pacific, I think the Russians would have quickly overrun most of europe to spain.
The soviet forces there were battle hardened, much of their equipment may have come from america but it was deployed in the field. (look up operation unthinkable, for an actual idea of what was discussed by churchill at the time)
In the short term England would probably have survived without an invasion of the island. the USSR would have had major difficulties controlling the french and germanys, as the USA wouldn't have stood by.
Without the Soviet declaration of war on Japan, a surrender would have been less likey. Launching an attack would most likely have encouraged the soviets to ally themselves with japan, and the US would have spent at least an extra year in the pacific, with a possible costly invasion of the home islands.
Meanwhile in the middle-east the soviets would have taken most of the useful productive areas of the birtish empire, up to India/pakistan, which may have held out (i don't know what militrary strenght lay there at the time) But soviet oil production would have sky rocketed, and they could have traded this for various other resources which they may have lacked.
In the long run i think atomic weapons and the US production capablities would have won out, however had the UK attacked without US approval it is entirely likely that the US would have gone with their original plan of allowing a seperate empire control europe the middle east and most of asia. (look at what the isolationist US were considering had Hitler remade Europe to his plans, US control of the americas north and south... pearl harbour made a difference, but Hitler was considered by many a lesser evil than stalin and communism, as Hitler's economic policies caused less difficulties for some americans.)