Comment by RobAley

"Plug in solar" (as "Balcony solar" is called in here in the UK) needs G98, not G99 approval and is free for plug in (<8kw). This is just one form to fill out, and the DNO can't refuse approval (assuming you fill out the form). Think of it more as registration than approval.

Current lowest costs from national retailers that I've found (been looking today as it happens!) is City Plumbing - £336 for 475w, £480 for 1050w (panels with 800w max inverter).