If they've got everything as they usually do when they arrive at that time of life. Why not get them a couple of rose bushes called Golden Anniversary, GoldenCelebration or other.
If you're going for something more expensive what about a holiday?
A photo album filled with family photos is lovely especially if you can write a commentary next to each one.
No doubt other ABers will have more ideas.
My folks have just had their 50th anniversary and we (6 kids) threw them a party at their house. We did buffet-type grub and we all brought 2 or 3 dishes each which was pretty cheap. We also did a few gold decs and balloons etc. They just loved having a party at home and I suspect if your parents are keen gardeners (as mine are) then a party at home might suit them too. Although their anniversary was in August we bought a gazebo from argos in case we needed it which worked out really well.
We also got them a hard-back copy of their favourite newspaper (the Times) for the date of their wedding. It made really facinating reading and they loved it too. It allowed you to put your own message on the inside cover and we wrote "Looks like you weren't the only thing happening in 1958. With love from . . . " !!!
50 years is just remarkable isn't it? Best wishes with your plans.
Thanks shivvy for sharing your parents anniversary. You have given me some great ideas. The newspaper is a good idea - will look in to that. I can't believe how amazing 50 years of marriage is!
Have booked out a room in their favourite country pub, and as it is in December there are plenty of gold decorations everywhere!
Thanks again