His name on his birth certificate is Peter McGhee, not McGhie, and he was born on 20 March 1868. Therefore on the day of the 1911 census he would have been 43.
There are three Peter McGhees and one Peter McGhie in the index to the 1911 census of Scotland. One is aged 41, two are 44 and one is 45.
The 44-year-old in Greenock and the 41-year-old in Govan can be dismissed because there are a 34-year-old in Greenock and a 31-year-old in Govan in 1901.
A 32-year-old in Bathgate in 1901 would match a 22-year-old in New Monkland in 1891, but does not appear in 1911.
That leaves two 45-year-olds in 1911, one in Peterhead in Aberdeenshire and one in Blantyre. Either or both could have come in from Ireland, or one of them could be your Peter with his age 2 years out.