Thanks
@Profpointy for actually answering the question that I asked.
It's pretty much what I thought, but with the number of legal people on here

I was just looking for some confirmation/reassurance that I was right.
I'm not a solicitor by the way, but have gone through the will writing thing recently. And I have done my homework on this. I did use a solicitor first time round as there were a couple of complications and to save time. I changed it slightly a bit later by editing in the new words and getting the new one witnessed. The standard clauses were copied from the solicitor's one.
Key thing to get right is the witnessing - witnesses must not be left anything whatsoever in the will else the whole will is invalid.
It is worth buying a book as it'll help guide you through the thinking you need to do even if you do use a solicitor (as I did for.the first version). Also helps you spot a solicitor who's bullshitting you - or gives you confidence he's not.
I would not use a will writing company or pre-printed form. I've done this in the past and though will was OK to be fair, it was clear I knew more about wills than he did .
For a straightforward will I'd just do my own next time