I think some folk are just listing inventions, which are really only a better kind of stick to hit things with.
The greatest achievement is the NHS.
The vision required to see a society that would contribute as they were able to develop and maintain a healthcare system that would last so long, treat so many in such a non-judgemental, we-don't-care-who-you-are-or-how-much-you-earn fashion is one of the greatest, most civilised concepts seen on the planet so far.
"We are not here in this world to find elegant solutions, pregnant with initiative, or to serve the ways and modes of profitable progress. No, we are here to provide for all those who are weaker and hungrier, more battered and crippled than ourselves. That is our only certain good and great purpose on earth, and if you ask me about those insoluble economic problems that may arise if the top is deprived of their initiative, I would answer 'To hell with them.' The top is greedy and mean and will always find a way to take care of themselves. They always do"
A Michael Foot quote, btw.