Hi Sarah,
One thing you didn't mention is how long you have had diabetes for? As mentioned I would not worry about the 4.3 (although I would not go to sleep with a 4.3 either). Sometimes when we get really good control like 4-8s our body gets used to those levels (I should really say our brain), and doesn't cause hypo symptoms because it's the 'norm'. Running your sugars a little higher would make it react stronger to the 4.3 when it happened but I personally wouldn't bother at that level. If you had a 3.4 then certainly but not really a problem with a 4+ imo.
Also if you have been diabetic for many years you will eventually loose your hypo symptoms, some specialists think it's due to nerve damage but recent research suggests that it's might also be due to the brain adapting to frequent hypos by increasing it's glycogen storage.
I lost my symptoms after having diabetes 32+ yrs but to date regular checking has been the best way to avoid trouble and seems to work well.
Frankie