I'd be inclined to hang fire for a while if your passports don't expire before Oct 05.
If there are no apparent rumblings about moving the goalposts for biometric information nearer that date, you could make your decision then. We had three passports due for renewal before Oct 05, so we'll be renewing all of them anyway, but we're waiting to see what happens before deciding on whether or not to renew DD's, as she has a couple of years left on it.
In answer to your question, as Celestine has said, it's going to be cheaper to pay £43(?) for a new passport than £75 (?) plus the additional time and expense of going to collect a visa. (Sorry, these figures may not be accurate, but it's a guess!)