Many thanks for sharing all this. Since you seem to know how the UK agents think, is locality of candidates a crucial factor for the agents? I live in the continent and had little luck whenever applied for UK based contracts, much more interest from the same UK agents when the contract position is based in my country. Is there a workaround to this, given that I'm perfectly ok with relocation?
UK agents definitely want easy. Either be in London or say you you are if you're not but canget there quickly (eg eurostar from Paris).
There is a practical reason for this. Once a position can be filled it is often filled very quickly. Getting a position can come down to who is available right now. This can even hinge on whether someone can be reached by phone that afternoon.
Also if you have a choice of interview slot, pick the earliest you can, later interviews will often get cancelled if a suitable candidate is found earlier. Companies don't want to waste time.
I got a job once that caused the next TWO DAYS of Interviews to be cancelled. This came down to being reachable by mobile phone and having access to a fax machine (this was 2001).