Although I normally recommend people use a local Insurance Broker, for Holiday Insurance I would recommend that you look at the comparison websites:
Compare the Market, or the Martin Lewis recommendations.
Obviously your ages, state of health and whether you want Single Trip or an Annual policy etc. will affect your premiums, and no one on this site can recommend the correct insurance provider for your particular demands and needs.
Granny grump ...I am presuming that your coach trip is not going out of the UK as it is only for two days,and if this is the case I am wondering why you would need this cover.
Your medical expenses will be free and your personal belongings could well be covered under your house contents insurance.
This leaves only cancellation of the booking cover which cost may be of a concern to you. If so then you will find an appropriate Insurer on line which could possibly save you some money.
Check your bank details and contents insurance - my friend gets holiday insurance through her bank account and I get fabulous cover through our contents insurance.
Where you are going to travel? You haven't mention about it. It is important to know where you are going to travel. If you are going to travel in EU then I suggest you to use http://covomo.com/. I found it helpful are price is reasonable.