A warm welcome to Beoworld!
You can buy the adaptors from Maplin as well as ebay.
I have a Beolab 1700 in my study, it's a nice unit, and sounds a lot beter than you would expect a 34-year old amplifier to sound! You may wish to complement it with a Beomaster 1700 tuner which was originally sold alongside it. They come up on eBay from time to time and as long as you are patient you will be able to pick one of for very little money, maybe £10 plus postage, and they look really smart together.
Simon