Agreed 400mn seems optimistic. Not really sure what to expect, but the lower they go the bigger the dilution - which longer term affects the value you can achieve at a new valuations.
It looks like they already have 30m shares issued, without accounting for share options, which are probably significant too.
Their last raise on Crowdcube was at valuation of £40m in December of 2018. Might not be the greatest crowdfunding return in 3 years, but at least it will become liquid with the opportunity to continue.
May be a ripe time to benefit from the interest in ESG investing though, so may gain some traction following the listing.
FYI - there is a separate discussion on it here (although limited activity so far):
Vote to see it on Freetrade if you haven’t already.