I have the advantage of belonging to the Northampton SF Writers Group (and the honour of being its vice chair), which is chaired by the author Ian Watson -- who has a 1st Class Honours degree in English from Balliol College, Oxford, has taught English at university level in Japan, Tanzania and the UK, has some 44 genre books to his credit and over 200 published short stories.
Having excelled at English throughout my schooling, I thought I knew almost all there was to know about the language until I joined the writers group. Ian is not the only member whose critiques and comments have helped my writing enormously, and I would not have achieved half of what I have without their input... and it's free!
(Well, £10.00 per annum if we're being pernickity.)