If you are not familiar with it, you should check out Lionel Challis' Peninsular Roll Call at the link below. It has abbreviated biographies of over 9000 officers who served in the British Army in the Peninsula. Here are some statistics regarding names from Ron McGuigan and my book: The British Army against Napoleon:

Most Common Family Names among Officers Serving in the Peninsular (Page 184)

In order of most common and the number of officers with the name:

Campbell 105
Smith 58
Stewart 57
Jones 54
Fraser 39
Gordon 39
Hamilton 39
Scott 39
Thompson 37
Cameron 56

Most Common Names among Officers Serving in the Peninsula

Alexander Campbell 9
Archibald Campbell 9
John Campbell 9
John Clarke 8
William Smith 8
William Jones 8
William Williams 8
John Armstrong 7
Duncan Campbell 7
John Fraser 7
John Hamilton 7
James Stewart 7
John Stewart 7
William Stewart 7

Most Common First Names

John 1305 (14.7%)
William 1024 (11.6%)
James 605 (6.83%)
Thomas 598 (6.75%)
George 524 (5.91%)
Charles 424 (4.69%)
Robert 395 (4.46%)
Henry 376 (4.24%)
Edward 290 (3.72%)
Richard 241 (2.71%)

Some Unusual Names

Hoylet Framingham Royal Artillery
Sholto Douglas 4th Light Dragoons
Alured Dodsworth Faunce 4th Foot
Sempronius Stretton 40th Foot

And My All Time Favorite

Christmas Knight 61st Foot