I’ve read a number of people say, observing the lack of growth of UK exports, that this illustrates how depreciations have little impact on trade flows these days. This is a classic case of reasoning from a price change. I think the phrase ‘never reason from a price change’ was popularised by Scott Sumner, although I got it from Nick Rowe.
The depreciation of sterling happened because of Brexit. Some of the depreciation might have been a result of the expected cut in UK interest rates, which means it should be temporary. The rest was to compensate for the impact of Brexit on UK trade. In both cases, therefore, exporting firms in aggregate get a temporary boost to their competitiveness (or profitability of trading), which will come to an end when interest rates rise again or Brexit actually happens, perhaps imposing tariffs or other costs that reduce competitiveness.
The temporary boost to competitiveness/profitability will be good for firms that already compete in overseas markets. But I learnt many years ago when I estimated aggregate trade equations that a lot of the effect from a depreciation comes from firms trading in new markets that they had previously considered unprofitable. To do that requires some investment: in distribution and marketing, for example. A firm is unlikely to make that investment if the gain in competitiveness is temporary.
This helps explain an otherwise puzzling feature of aggregate trade following a depreciation that - unlike Brexit - leads to a permanent improvement in competitiveness. It takes many months before the full improvement in trade volumes comes through. If it was just a matter of goods getting cheaper and people buying more of them you would expect a fairly instantaneous impact, but if firms are having to invest to expand markets, the full impact will take longer to come through. 
In the case of Brexit the gain to competitiveness is temporary. It is a mistake to start with the depreciation, and then be disappointed by the lack of any reaction. Once you ask why there has been a depreciation, it becomes clearer why any gain to exports is likely to be modest. 
 As tariff changes are perhaps likely to be more permanent than exchange rate changes, this may also help explain the puzzle discussed here.
 This argument apart, one other thing you quickly learn if you monitor aggregate trade is how erratic it is. We will not know for sure what the impact of the Brexit depreciation has been until well after Brexit itself.