I want to add a money market fund to my portfolio as a stable, low-risk component, but I don’t know much about these kinds of funds.
It looks like I currently have a simple choice between two options: CSH2 and XSTR. Can anyone enlighten me on the pros and cons between these two funds? Thanks! 
As far as I know the biggest differences are that one is accumulating and the other is distributing. CSH2 also has slightly lower TER. I dont see any reason not to go with CSH2. It is all round better IMHO
Accumulating funds are best used in an ISA - otherwise it’s a pain finding out the excess reportable income (ERI) for tax purposes; Accumulation units – tax on reinvested dividends UK - Monevator
Using distributing mm funds in a GIA requires thought depending on wether you want capital gains or interest income