The Loegrish language has (or has had) a few different dialects and a standard version. This is an overview of the major differences between each dialect.
The dialects + standard
Midlands
The Midlands dialect is spoken from the Welsh Marches to the coast of the North Sea, and from southern Yorkshire south to the Thames. It is roughly spoken in the area once known as Mercia, hence the Loegrish name Meirċyg (“Mercian”). It is divided into West Midlands and East Midlands, which are sometimes classified as different dialects.
Overall, what separates Midlands from the other dialects of Loegrish is that it has more Norse and Latin influence (in the East Midlands dialect); it is closer to Welsh and Cumbric (especially West Midlands and in Yorkshire and Humber); there is a more rigid distinction between voiced and unvoiced fricatives than in other dialects; [xw] instead of [hw]; and earlier development of [y] to [ɪ] and of [ɑː] to [ɔ].
The line between West Midlands and Welsh is somewhere in the Welsh Marches, but it is very blurry and some speakers mix Welsh and Loegrish.
Wessex (Orlechwiddyg; Bilġyg)
The Wessex dialect is spoken in Wessex, east of Somerset, and west of Essex. The Loegrish name comes from Orlechwidd Galidin (Old Loegrish: ƿorlechwið galédin), referenced in the Welsh triads as Arllechwedd Galedin. The other name, Bilġyg, references the Belgae tribe of Celts, from whom much of the Wessex Loegrish population are descended.
East Anglian (Iċenyg)
The East Anglian dialect is spoken in the area known as East Anglia. Its Loegrish name, Iċenyg, references the Iceni (Iċen), the Celtic tribe that Boudica (Báddig) belonged to. Loegrish speakers sometimes call their language “the language of Boudica” (hin yeith Bháddig).