I'm sure this is very simple and I'm missing a trick or something, but all I want to do is write something in a memo, click a button to save to a textfile and then be able to change the memo, click the button again and add what has been changed onto the text file (like an append)

Just so you know, might get quite a few more questions thrown this way over the next few days/weeks

Any help appreciated, thanks. Hopefully I didn't break any forum rules

Start by looking at Memo.Lines.SaveToFile() , if you want to append to an existing file, have a look at SaveToStream . The latter is IMHO easier to use when appending, because you can first load an initial file into it, and then pass it to the function.