Victoria I don't suppose you bought the Binatone Marina 300's did you? I'm looking at buying them just now for the other half and I keeping in contact on the slopes.
We use unlocked mobile phones on a local Sim card. Makes it cheaper for staying in touch with the UK, as well as being easier to text in noisy bars. Depends who you meet up with aswell. It's easier to arrange a meeting time with new friends by text rather than hope that WT are compatible.
I would suggest that if you are intending using Walkie Talkies you get 8 mile radius as a minimum. The mountain do block off part of the signal and you may have trouble receiving the signal if you intend using a weaker pair.
Have used them for several years in Pamporovo and find them perfect.
We bought Tevion Terrain 550 walkie talkies from Aldi for about £25 (seemed identical to another Binatone model). These had an 8 km range and worked very well. As mentioned previously, you can receive some confusing chatter from others on similar frequncies. One word of advice, make sure you switch them off at night, or the crazy chatter & bleeping will drive you nuts!