I just tried to use tickets.railforums.co.uk to try to buy a ticket from Luton to London Thameslink, as that is the ticket type (super off-peak return) that I most often get, whether I specify say St.Pancras or Blackfriars as my actual destination. I don't always know at the time I'm buying the ticket where it will be most convenient to get off - that depends on which tubes happen to be working at the time. I really don't want the ticket-selling site to tell me all the possible train times as I already know them (yes there is a new timetable this week but it is barely changed). So I thought that by selecting this virtual destination I could stop it providing me with unnecessary informaton and cut out a few steps in the purchase process. London Thameslink is a valid destination in the drop-down list, but when you try to buy a ticket to it you get one of two errors - either "no results were found for your current search" on the new site or "HTTP 422" on the old one, which I also tried. I suppose that's a slight improvement. But if you can't actually buy a ticket to London Thameslink it would be sensible to not have it on the drop-down list of possible destinations.
It would also be nice to know if therer is any way of buying a simple off-peak return without having to specify which actual service you are going to use: the rail ticket machines at stations don't insist on you doing this nor do staffed ticket offices, if you don't mind queueing up for one. So it is annoying that nearly all the websites that I know about insist on one choosing a specific outward and return train before allowing a ticket purchase. This one more way in which rail ticket selling could be made easier.
It would also be nice to know if therer is any way of buying a simple off-peak return without having to specify which actual service you are going to use: the rail ticket machines at stations don't insist on you doing this nor do staffed ticket offices, if you don't mind queueing up for one. So it is annoying that nearly all the websites that I know about insist on one choosing a specific outward and return train before allowing a ticket purchase. This one more way in which rail ticket selling could be made easier.