oddbean - is ther one one cfuk with lelit flow control and combo with grinder? (Maybe grinder has been sold now, I don’t visit there often).
If memory serves me right, the Beta machines were sold for £450 (edit: actually £848!) or thereabouts - a real bargain. Rob1 has one (I think) and is really happy with it.
If the one you reference above has a lelit flow control fitted, that’s worth £200 or thereabouts (maybe less second hand, providing its been looked after) alone.
If you are buying any machine…. You have to either trust the seller, based on reputation, or at least go and check the machine over yourself before parting with your money.
When I sold my machines, I always made sure I met the buyer and, when possible, demonstrated the machine through out, made a few coffees to make sure they are happy with the sale as much as you are.