Hi David and welcome to the club!
I bought mine last March and have done lots on it (small scale titivation) since I got it. I cant comment on the seats, but I did change my seatbelts.
My car was built in 1967 and did not have belts from the factory, so one of the earlier owners had fitted lap belts (not inertia reel), these were white (well mucky grey by the time I got the car) so I wanted to change them. I did some research and found a company (which I will post details later) who custom make them. They can make anything you want, lap belts, inertia reel, stick stalks, sockets on belts, any colour, any buckle, chrome or black finish buckles etc, etc, - they were brilliant.
I will add a photo of mine tomorrow along with details of the price etc.
They werent cheap, but I can highly recommend.
I didnt go for inertia reel as to add these you have to do quite a bit of alteration and my car is highly original, in addition unless you fit the reel under the parcel shelf (which can cause snagging) then the reel goes on the floor behind the seat, which limits the distance you can put the seat back (so I believe) and I am 6 ft.
I hope this helps.
Mark.