As I do not reload I am reliant on factory ammunition, but there seems to be such a choice that I am, frankly, somewhat baffled. What is your expert advice?
First, you must ensure that the cartridges you use comply with current legislation.
Because you are using your rifle in England, loads need to have an energy of 1,700 ft/lb, but not all barrel lengths and bullet weights meet this requirement in .243 calibre.
The bullet itself must be of an expanding type, so a hollow or soft point bullet is required.
This also applies to plastic tips, solid copper and lead-free bullets as long as they are designed to expand.
The problem arises when one comes to choose from soft point, hollow point and so on, as each type, dependent on design and bullet weight, can perform differently.
Too light a bullet with a faster velocity and a high expansive head — for example, a ballistic tip — can cause a great deal of meat damage, especially with a .243.
Too much weight and a slower velocity may not expand the bullet fast enough and simply punch a neat hole straight through the beast with little energy imparted into the vital regions.
I would suggest you try several boxes of each type to see which results you favour.
However, the accuracy of any particular load you choose is paramount as one should always strive for a well-placed shot.