Does anyone know of an audio adaptor kit, which preferably doesn't cost the earth. I have tried the usual suspects (Maplin, CPC etc.) to no avail.
Any ideas?

Many thanks

What is it that you want to convert from / to ?

There's probably 100s of possiblilities so you need to narrow it down a bit.

I have an old mic bag that has all kinds of adaptors and get out of jail free cards that I have built up over time. I would say that is your best bet. Having said that it can turn into quite an expensive pastime but it is worth it when you pull the wangleon to widgetLR converter (balanced of course) and save the day

I was looking for various mixtures of XLR/ 1/4" jack / 3.5mm jack / phono really. I'm sure I have seen a boxed set in the past somewhere...

Canford stock kits like this one
Product code 49-299. They do a few other kits as well. Not particularly cheap, but all good quality.

If you have money on your hands then the Canford kit above is your best bet, whereas if you have time on your hands you may be better off spending an evening or two at home with your soldering iron making up a whole bunch of short leads......

IMO the short leads route is preferable to the adaptor route because many types of adaptor place far too much weight and/or leverage on the connector. Eg. XLR + adaptor into phono socket = two fairly heavy plugs with 3-4" of adverse leverage on a socket that was designed for a plug weighing 1/4 as much with 1" of leverage. Given an adaptor with 6" of flexible lead on it you can usualy arrange for the weight to be taken by something other than the socket, like the table or the next unit down in the rack, etc.

Just my thoughts though.

I'd second the spend a while and make them idea. Remember, you don't necessarily have to solder all the connectors, if you want Mini jack to 2 normal jacks and mini jack to 2 XLR's you could get a pair of cheap (less than £1) insert leads and chop the jacks off one and put XLR's on to save time. I also use mic bags for my adaptors and jumpers etc.

One tip! Keep a check list of what you have, and every so often, go through them and check they're all there. There is nothing worse than needing something, thinking "aha!!! I have just the thing", and then finding it's missing in action.

I have 2 complete sets of the rare everything to everything combinations (which includes at LEAST 2 of each per set) and then a spare set of AT LEAST one of each. That way, when something walks it's easily replaced whilst prepping and a replacement "spare" can be made or purchased without the rush.

Standard stuff like XLR and Jack gender changers and Jack to both M and F XLR's I have piles of. These get placed onto the necessary leads during prep, the sets of adaptors are for last minute / extra / odd stuff you haven't been told about.