"Do you think it would be true to say that the english spoken in England is as much a dialect of english as the dialect spoken by the Lowland Scots?"

There is no single Lowland Scots dialect as such but there are various dialects of Lowland Scots in Scotland and some of them are quite differnt from each other. Among the more individual are Shetlandic; the Doric of the North East; and my own Borders dialect which many call the 'yow an mey' dialect. There are various dialects of English spoken in England too of course. But yes I take it you are meaning standard English as spoken by many newsreaders etc. That too is surely a dialect. Basically I imagine any living form of speech is a dialect.