Whilst I have not yet refurbished my Murena seats, I have made new bases for my Lotus Elan +2 seats. I did not use manufactured seat foam, instead I purchased foam and formed the bases individually.
Foam can be purchased in varying density, I used a firmer foam for the side bolsters and softer for the seat, the foam can be built up in layers to get the rough shape - I just used a spray contact adhesive for this. Once I had the rough shape I then trimmed further with a sharp carving knife, finishing off with a sanding disc in an angle grinder - this bit is best done outside as it is a pretty dusty operation.
Making the seat foams does not take a great deal of time and is also not expensive!
You can also use foam to repair/improve your existing seats if the bases are not too crusty.
Cheers
John

