The photo doesn't magnify well, but at a guess, its Box (Buxus sempervirens most likely, but possibly Buxus microphyllus); consider whether you want to fill in with more plants because there are so many diseases and infections in Box these days, perhaps that's why you've lost some of the plants already. If so, depending which particular affliction they had, you may find the rest of those you have succumb too.

I wondered if it was on of a small leafed Lonicera, such as Lonicera nitida.

Could it be a privet? Maybe variegated? Ask passing neighbours---someone will know! Or send a closeup photo to this site of just one branch showing the leaves more clearly. If not, take a branch to a garden centre and ask. Most have one person whose job is to know his/her shrubs!
If all else fails, replace with something such as hawthorn, which is excellent for supporting insects and birds.

Pretty sure its neither Privet nor Lonicera - leaves aren't large enough for privet and the growth habit does not fit with Lonicera nitida. A closer, higher resolution photo might confirm or deny ID

Like Bamboo, I thought Buxus but the only other shrub that I could think of would be Luma apiculata. I also can't get a good magnification.

Thankyou all for taking the time to reply to my question, solved it today after the reply that it was possibly Box, I went to the garden centre and now knew where to look and there it was, The hedge has now been repaired, Thankyou once again .