Hi we think we're going to be putting the defender up for sale pretty soon but we didnt get a manual when we bought it. Reckon the mother in law threw it out is it just a case of ringing Land Rover and giving the reg ?
Also no idea how to value it, if I put up pictures etc on here will I get a load of look on ebay type abuse I can take it lol

For a valuation, try the Land Rover Workshop Defender Ebay search thingy https://defender.lrworkshop.com/for-sale
It may give you some clues.

Keep the defender and get rid of the mother in law.

Col

"Hi we think we're going to be putting the defender up for sale pretty soon but we didnt get a manual when we bought it. Reckon the mother in law threw it out is it just a case of ringing Land Rover and giving the reg ?"

What manual..... owners handbook or service book?
Handbooks are available new & secondhand, you don't give any details of the model, year or engine but armed with that data a quick trawl of the usual places (Ebay, Amazon etc) should come up with an owners manual.
If it is a service book then no, LR won't supply one but if it has been (main) dealer serviced then the history should be on record. Do you not have any receipts to show the service history?