Smallest, cheapest device to connect with wire to printer.

Our iPad may or may not wirelessly connect to our printer for no reason at all.
So as above ,we need a titchy little thing just to connect with a good old fashioned wire to print out invoices.
Space is a real issue so a cheap second hand laptop is not an option.

No better buying a compatible wireless printer?

Plug the printer into the router. If you have wifi, you likely have one of these already.

MLC ,more info please. On iPad it says NO AIR PRINTERS FOUND. Would plugging into the router get around that problem?

No, AirPrint is a protocol(sort of) the printer needs to support it. Just having a wireless printer won’t make it work with the iPad.

There might be a device like a print server to enable AirPrint or you could go the DIY route and build one from RaspberryPi

http://www.lynsayshepherd.com/blog/2013/01/14/wireless-printingairprint-server-via-the-raspberry-pi/

It is an air print printer some days it works , some days it doesn’t. Just need something we can depend on.

Or use something like Smart Office 2 which ignores Apples printing stuff and does it’s own thing which lets it print to non-AirPrint printers.

Well, it depends.

A. Lots of printers are USB only. If that’s the case you can’t just plug your network cable in.

B. If your printer does have a wired network connection, just run a cable from it to the back of your wifi box where there’s sure to be a socket for it.

Back to A, though. Put one of these between your router and your printer.
http://www.serversdirect.co.uk/TP-Link_TL-PS110U_Single_USB_2.0_Port_Fast_Ethernet_Print_Server_TL-PS110U/version.asp?refsource=SDadwords&crtag=SD&gclid=CIfKi9bcqsICFU6WtAodHUUAtw

Disclaimer: Whatever’s causing your current setup to not work might kill this one too.

It is an air print printer some days it works , some days it doesn’t.

Ah. That’s odd. Sounds like your best bet is to get that sorted.
I’m not aware of any cable you can plug into on iPad to print with. That would require you to install printer drivers etc which isn’t really the iPad way.

I’ve got a USB printer plugged into a desktop. Desktop runs airprint as a server service, iDevices print through it no problem. It was a bit of a frig to get working though (there’s a registry hack, on XP at least).

What I’m thinking of is one of those little note book thingies. A lot of them you can’t connect to a printer, so just wondering which ones do.

We’ve got a £40 HP printer at home that’ll print from phones, tablets, PC or laptop either through the WiFi or by sending stuff to it by email.

Sounds like an ideal job for a Raspberry Pi to me.