Thames Islands  应该翻译为：泰晤士河群岛。

1. Islands 是复数，故译为“群岛”； 

2. 这些小岛就在泰晤士河上，所以，名称要体现出“岛屿的归属”。

下面这段文字讲的很清楚：

Eyots and Aits — Thames Islands，by Miranda Vickers. The Thames has many islands. Miranda has undertaken a review of all of them. She will tell us about those of greatest interest.

Eyots and Aits：小岛和河中的小岛