"Meths" is ethanol + methanol + purple dye + pyridine.
If you search, you can easily find it undyed (even in the UK), which is good for blonde shellac. If you search harder (and sign paperwork) you can get it without the pyridine, which avoids the horrible smell.
If you live outside the UK and our alcohol-funded tax system, then you can afford to buy strong drinking alcohol like Everclear or some vodkas. These work fine and are less toxic - even methanol fumes are a nuisance on a hot day in a small volume.
If it's hot weather, especially for a dyed shellac like piano or coffin black, then try replacing some of the ethanol with isopropanol (isopropyl alcohol) instead. This is less volatile and allows a longer working time. Black can be like treacle in this heat.
In the UK, you can buy isopropanol OTC from Boots, but they've recently started getting suspicious about it, because it's a precursor to Sarin. It's a precursor to almost every industrial chemical process in the 20th century, but don't let rationality get in the way of the great easter-egg hunt.