@Rick, many thanks for posting that -- I was unaware that you could move a GV number to another account and preserve all the associated data.
@Tangible, IMO both Callcentric and Anveo are high-end PAYG providers with excellent quality, reliability and support. Callcentric has been around more than ten years, while Anveo is a relative newcomer with about a two-year track record. As you would expect, Anveo has more aggressive pricing. Both companies allow you to make calls with any desired outbound caller ID, once you have verified ownership of the number in question. Although Rick's suggestion solves the main problem at your summer home, you may still want Anveo or Callcentric service there, e.g. for 911, as a backup, for better rates to a frequently called country, or for a feature not provided by GV.
Possibly, you may want to replace your Comcast voice service with a combination of GV and another provider. With proper configuration of two OBi devices, you can make and receive calls on the same GV account from either location.
With your existing Comcast service, you can make outbound calls showing your GV number in several ways: You can dial the GV number and at the main menu, press 2 to make an outgoing call. Or, from the GV web site, you can click on a voice message, history entry, or contact; your Comcast phone will ring and upon answer your party will be called. There is also a Call button, useful for calling a number not yet in your GV records.