I gather you are simply looking for the cheapest you can get.
There is generally a reason for being the cheapest . Though it's possible Vodafone are throwing money away to buy market share.
From congestion complaints I see on these forums I personally wouldn't touch them. Assuming Lewes is the fibre headend exchange, (suggested by MrSaffron), Vodafone do not have an LLU presence there if samknows is up to date. That could mean they are using BT Wholesale backhaul, and it seems to be on such exchanges the Voda-congestion mainly arises. BTW backhaul is vastly more expensive than LLU backhaul.