How to calculate foreign exchange effect on investment - Newb question

Hey there, I am Australian looking at a stock listing on Trading212 the Vanguard SP500 that is listed on the London stock exchange denominated in GBP, but the underlying assets of the fund are US based companies. If my understanding is correct, I am exposing myself to two forms of exchange risk. The first being AUD/GBP, and the second being the inherent GBP/USD because of the underlying fund assets.

My question is, how would I calculate the exchange rate gain/loss of the two currency pairs in 12 months time to determine the actual return of the investment? Is it AUD>GBP, GBP>USD upon buying then USD>GBP, GBP>AUD upon selling? If not, why wouldn't it be so?

Note. I am aware that SP500 is available as a fund in Australia but am curious about the exchange implications nonetheless

Here is some information I have gathered elsewhere.

" The net exchange rate risk you're exposed to is just AUD/USD. You calculate your gains in AUD (for example, for tax purposes) by using the historical exchange rate between AUD/GBP and the historical prices of the stock in GBP." " This is exactly the point – even though the ETF is denominated in USD, the investor is exposed to JPY rather than USD. This works as follows: the investor converts EUR into USD to acquire ETF units. However, the fund manager, in this case iShares, has a mandate to invest in Japanese stocks, which are denominated in JPY. Therefore, the manager will convert USD into JPY to purchase securities. This way the investor becomes exposed to JPY instead of USD.

As an example, let’s assume EURJPY exchange stays constant, whilst the USD depreciates by 1% against both EUR and JPY. This way, the value of ETF investments increases by 1% in USD terms due to JPY appreciation. However, from our investor’s perspective, the USD depreciates 1% against EUR, leaving the value unchanged in EUR terms."