Regarding the part numbers given in my spreadsheet, it seems that I've mistakenly managed to mix up companies (due to the way I order parts through my University). What that means is that part numbers which are all numbers are, as stated, all from Farnell. Part numbers beginning with "SC" however, are from another company, which is connected to Farnell, but which is in fact called CPC (cpc.farnell.com). The only thing which this might affect is minimum orders. I've only ever ordered through the University side, which has a minimum order value of £20, but I can order from Farnell and CPC in one transaction. If you can't, that might cause potential problems... The easiest long-term solution is probably to find the equivalent parts from the other supplier, such that they can all be ordered together.
Sorry about that!
Adam