Haha Kerry!
Thanks for the link and the reply.
Well, I managed to get some help earlier in the day from another site, as after I posted here I realised that JaneK had asked a similar question back in June without a reply. To delete gedcoms, you need to open your tree then go to "Manage". Then just click delete.
To delete an account they make you write an email, and I have done so, but I have had no confirmation yet.
It will be an interesting battle if they retain my tree data, as I have heard some sites do...
Nina