When an LGCIU declares itself faulty it does't mean it is unpowered. It only means its outputs are disregarded by users. But the gear down locked output from LGCIU 1 is hardwired to the panel indicator and as long as the LGCIU has electrical power it will provide the down locked indication. Not so in the ECAM WHEEL page.
If you have a double LGCIU failure and on top of that the LGCIU 1 happens to be unpowered, then there is no landing gear position indication. There is no way to be certain. Gravity extension should work normally. The down lock springs should help to extend the lock stay to overcenter. But of course something abnormal could happen and you wouldn't know.
So in that case you should use your airmanship, take into account fuel and time and all circumstances before making any decision. With fuel and visibility you can make a low pass and have someone take a look, or even (why not) request air force airplanes to inspect it from below. Or you can study the abnormal landing gear procedure and think of a contingency procedure should things con bad after touch down