The Bristol Channel - Somerset Levels ice lake

 https://doi.org/10.1016/j.quascirev.2017.05.019

This  deglaciation paper  (which is also open source),  includes some analyses of the subglacial and proglacial meltwater routing associated with the LGM reconstruction.  Interestingly in this model, subglacial meltwater is able to flow up the Bristol Channel into a dammed proglacial lake on the Somerset Levels, which then overflows southwards towards the English Channel.  The route is probably assumed to be via the Chard Gap, about which there has been much discussion over the years.......

Deglaciation of the Eurasian ice sheet complex
HenryPatton et al
Quaternary Science Reviews
Volume 169, 1 August 2017, Pages 148-172

A more detailed analysis of the "Lake Maw" problem is here:

https://brian-mountainman.blogspot.com/2018/12/more-on-lake-maw-somerset.html