Dell or computer experts

You could try to search for a wireless keyboard.

You could try to clean up your laptop.

Remove temporary files
https://www.techradar.com/news/the-best-free-alternatives-to-ccleaner

Use msconfig to disable some of the unnecessary programs that automatically load on start-up
http://netsquirrel.com/msconfig/msconfig_win7.html

Download, install & run spybot to remove malware
https://www.safer-networking.org/dl/

Also, check how full up your disk drive is. If's it's got more than 75% used, delete some unwanted stuff, or back the files to another drive. e.g. a usb drive,  or your google drive (if you use gmail) or your bt cloud (if you use bt internet)

on screen keyboard

stow_judge

I've done all that. I even reinstalled a fresh Windows. the problem I am getting is when using MS Word, every so often it will lock up very temporarily and while I am typing it misses out certain words I am typing. I've tried disabling settings in MS Word such as auto correct etc but it doesn't change it. I thought a fresh install would help but it didn't. I am considering changing the hard-drive because it might be that but then it only seems to happen when Word is open so it could be a Word issue I've tried everything else. I'll keep looking for keyboards

Try searching for "compact USB keyboard" - This should show a few keyboards with keys tightly spaced?

Yes. Compact keyboards, as @Gin says. "10 key less" (ie without the number key block on the right) is another term to be aware of.

Check the placement of the non-standard keys as they can move about between keyboards, and that you get a UK layout (or whatever country is appropriate).

You could start with Dell themselves:
http://www.dell.com/en-uk/shop/keyboards-combos/ar/6592?~ck=bt

You could try the market. Lots of Dell boys to be found down there.