A google for In line cable connector will bring up many suitable products like this. Ups sorry links don't work. They are small rubber or nylon boxes with cable grips. The main thing is some resistance to splashes and cable retention. The IEC 13 plug and socket would be what I would use.
I tried to give links but pre-view is not showing them maybe someone can point out what I have got wrong?
ELECTRICHELP
if the microwave has a pre moulded plug , thats intergrated into the flex , as with most type of domestic appliances brought nowadays , the information states that removing this plug arrangement invalidates the warenty on the product.
When I google in line cable connectors I get stuff to do with TV aerials (!) - please could you post a link to the one you mean?
I know the warranty will be affected (it is a pre-moulded plug) but the microwave is old so it doesnt matter.
Would the junction box not be okay if, once correctly wired, I tape it all up with insulation tape? I have a spare junction box lying about so this would save having to buy anything else - just wanted to check it was safe? It's a 30Amp one which I think is the correct sort.
Whole range shown here (Google "uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&binCount=15&Ne=4294957561&Ntt=in+line+connector&Ntk=I18NAll&Nr=AND%28avl%3auk%2csearchDiscon_uk%3aN%29&Ntx=mode%2bmatchallpartial&N=4294965277+4294954945&Nty=1") I would not go to RS myself but it's a good web site to show all the different types.
These (Google "ba.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0531431") are what I have used in past normally have a few in stock.
See also here (Google "cpc.farnell.com/duraplug/lcp103-whi/lead-connector-3-pin-white/dp/PL10426") note these (Google "cpc.farnell.com/schurter/r47320000/rewirable-iec-mains-connectors/dp/PL06086&crosssellid=PL06086&crosssell=true&in_merch=true&") which means you can use kettle lead to extend.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!