As you guessed, the returns of the currency etf are supposed to closely match the returns of the currency the price level is mostly irrelevant. The 3x leveraged etf is supposed to closely match three times the returns in the currency. So for example if the return of the spot was 2% the first ETF should return about 2% and the second about 3 times 2% = 6%. However, the numbers above are not exact for important reasons.
In this case and generally currency etfs do not hold the currency but hold currency futures, forwards or swaps designed to get you returns closely related to the currency return. They are designed this way as it is generally a better deal than the costs of just holding the cash, but this does mean that over long periods of time they will drift a bit sometimes in your favor sometimes not.
Leveraged ETFs use similar instruments and currency options as well. Tracking a leveraged index is much more challenging and generates very large costs which are passed on to the investor. It's not uncommon to see an index be flat but have both the leveraged long etf and the leveraged short etf lose a lot of money. This is why, as @PabTorre mentions, leveraged etfs are generally better for very short term investors.
Your calculations are correct on the amount need to fully hedge your investment. Though I wouldn't recommend using the levered etf for anything but the shortest term hedging. Also, it is worth considering whether the opportunity cost locking up money in currency hedging is worth it instead of say having investments across multiple currencies or using currency-hedged etfs (if available).
Edit for comment:
Neither currency etfs or futures/forwards are particularly good for hedging as a individual investor. Institutions generally use futures and forwards but they often have to put down less than 10% of the value to start so they can cover 30k using only 3K or sometimes nothing. You can check your broker but I doubt this is anywhere near the case for most individual investors. Also, futures/forwards need to be rolled which adds a lot of complexity. For individual investors generally the best option for hedged equity is currency-hedged equity etfs where the do the hedging for you. Sorry for the USD-based example, GBP versions likely exist but check with your broker about liquidity.