The general consensus is that the British Army was a good fighting force but was badly led at the highest levels. It was also, of course, hampered by the extreme length of its supply lines and by the size and relative lack of development of the country in which they were fighting.
Historians say that the British Army fought very well. Their soldiers were brave and well disciplined. The real problem was with their senior officers and with the government that directed their actions and arranged for their support. The general officers often put them in bad situations and the government spent too much of its time on bureaucratic infighting. When this was added to the problems of fighting across such a huge expanse of land, with no real cities that could be captured to end the rebellion, the problems the army faced were immense.
Basically, you could say that the British Army was good on the tactical level but was let down by those responsible for its strategy and its logistics.