Once you've been accepted to LSE, you may apply for housing. You will have several options, but prior HC students who attended LSE recommend the following:
Bankside House - most recommended
Rosebury - most recommended
High Holborn
Urbanest Westminster
You are welcome - encouraged - to apply for a single, ensuite room while at LSE. The amount you are charged for housing by Holy Cross during your academic year abroad will remain the same (i.e., as if you were actually staying at HC).
Some residence halls include catering, while others do not. Depending on where you live while at LSE, you may receive partial board (some meals,) or none. In either case, knowing the cost of food in London is helpful to prepare a budget accordingly. Use the Numbeo website to help you calculate the current price of basic items, and dinners out.
Check out the website Numbeo:
https://www.numbeo.com/cost-of-living/in/London?displayCurrency=USD