This initiative consists of a letter that has already been sent to the leaders of Labour and Lib Dems asking them to be courageous enough to form a Remain Alliance. Grassroots for Europe has receive no reply to date,. which is not surprising as each party has to play its party games. But the more that this letter can be put into the public domain, by writing to local and national press to draw attention to it, the better.
See these materials: https://ukpen.eu/campaign-material/group-letter-to-corbyn-and-swinson/