I was advised by the suppliers of my machine to contact the UK warranty centre (it has a three year on-site warranty). They, fortunately, took a different view to the US on-line "support" and sent out an engineer with a new keyboard and a refurbished motherboard. As it turned out the clip was not broken just dislodged, he solved the whole problem in less than 10 minutes and used no parts. I am very impressed by the UK Dell service!
I feel a bit stupid and cack handed but all's well that ends well. I was very pleased that the Dell warranty call centre decided that as I was following Dell instructions to change a user replaceable part (the disk) the problem I caused was covered by the warranty. Much better than the offer of a $354 replacement motherboard from the US operation.
is a great improvement. Silent machine and a fair bit nippier!