Back from Namibia now more's the pity.
Just a quick thank you to Mark, Adrian, Ricky and Lance for their help and advice as per the subject of the thread. It was much appreciated Gents and thank you all very much.
My experience taking firearms was as follows for anyone interested in the future and if this thread turns up in a search.
Arrived at Heathrow with three hours before my flight left.
I took hand luggage, my suitcase, rifle case and ammunition box.
I had checked in online, so scanned my passport and mentioned to the guy who was helping passengers that I had a firearm to check in.
He pointed me to an empty desk where the young lady took my suitcase and weighed my rifle and ammo.
Another member of staff arrived and said to waive the excess baggage charge.
My suitcase had gone and they slapped 'firearms' labels on my rifle and ammo cases while calling for another member of staff to come and collect me.
I was directed to wait for the person to come which should be about 15-20 minutes.
I stood just away from the check in desks and 20 minutes later a guy arrived and took particulars from my firearms licence and gave me a surrender of weapons form.
He went off with my rifle and ammo and said to go through security and meet him at the Border Force office which was in the departure lounge along a corridor by Dixons.
Security check for myself and hand luggage complete I found Dixons, went up the corridor and met the guy at the end.
We waited for a Border Force officer to arrive at which point I was directed to a small room.
She asked me to open the case and she took the details of the serial number from the rifle and matched it to my licence. She didn't look at the bolt but I invited her to and then she did.
She asked how many rounds of ammunition I was taking and I told her I had 80. She checked against my firearms licence and saw that I was entitled to hold 300 and decided that because I was taking less it was all OK. She didn't even want to look and I had the impression she wasn't entirely sure what she was doing.
I was issued with necessary paperwork and it was all done. Dead easy and the only paperwork I had to produce was my firearms licence.
Everything was checked through to Windhoek but I double checked the labels provided were correct and were marked for transit through Johannesburg.
I arrived in Windhoek the following day after an easy transition through Jo'burg.
Filled in the immigration form and progressed through.
There is a small grilled hole in the wall just as you go through to baggage reclaim with an illuminated 'Firearms' sign. I took a quick look and saw my rifle and ammo cases there so decided to claim them before my suitcase.
After waiting for ages, there were a party of Americans in front of me all with about three firearms each I was able to claim my gun. A quick check of the serial number on the rifle and an import permit issued and I was away. Still hadn't had my ammo checked.
My suitcase hadn't arrived so had to fill out a baggage claim form and left the airport hoping it would turn up soon. It wasn't really a big deal as I had a change of clothes in my hand luggage and was wearing my hunting boots and bush jacket. It arrived the following morning so no major inconvenience.
On my return journey I turned up at Hosea Kutako and joined the queue to check in. My suitcase went on it's way and they issued me with some tags for my rifle and directed me to the Namibian Police office which is easy to find, just on the right as you enter the airport.
After waiting for a while with a couple of Italians an officer eventually turned up and we completed the formalities, a check of the serial number and I sealed my case and he attached the tags which I checked were for transit through Johannesburg and issued my paperwork. I had left my spare bullets with my hosts so didn't have an ammo case on the return journey.
I took the rifle back to the check in queue and waited briefly in line before someone directed me forward and took my rifle off me and it was gone.
At Heathrow after baggage reclaim I headed down the red channel and said I was here to claim a firearm.
As I got my paperwork ready it arrived and after checking the serial number again against my firearms licence I was on my way.
It really couldn't be easier and I had absolutely no problems with the process. The only paperwork I had checked was my firearms licence. No-one asked for a letter of invitation or anything else.
It wasn't as daunting as anticipated and if anyone is considering hunting Africa and wants to take their own rifle I would recommend SAA as they don't charge and it really is so easy.