Also wanted to add a bit of off-topic (in regards to the prices you mentioned); as per the Pricing UK Securities, UK (London Stock Exchange) is the only exchange in the world pricing its securities using currency subunits (pence instead of pounds)
Being a US index, S&P 500 is not quite related to GBP in any shape or form. Moreover, the figure you see on the screenshot (2914.04) is not USD either, it is an arbitrary “points” figure that kept growing since 1923 when S&P index was only created (it did not even have 500 companies in it back then).
If you were to buy the S&P 500 index tracker - you probably would either go for the US version SPY (priced at $291) or the UK version VUSA (priced at 4254p or £42.54) Whilst the prices are substantially different - it makes absolutely no difference since they both track identical companies as per the index algorithms. The only reason why their growth will differ is the volatility of GBP/USD conversion rate which British Pound is exposed to.
Just wanted to make sure your week has been absolutely enlightening 