The number of searchable on-line records has grown considerably since I started my research and they continue to grow.
Many birth, marriage and death records can be found on the FreeBMD. The online records aren't yet complete- but a good proportion of Gunnee entries can be found and the list continues to grow. The website is particularly useful in narrowing down potential marriage partners. A marriage record for an individual includes the reference to the location in the original register. Clicking on the page number will show all the other entries for the same page. From a search for a groom a list of three potential bride's can be found. Assuming there are subsequent census records it's often straightforward to confirm the bride.
The Church of Jesus Christ of Latter-day Saints (LDS Church, or the Mormon Church) have invested much time and money in developing the database on FamilySearch. Whether or not you agree with the reasons for the database, it remains an enormously valuable resource for family historians. The searchable records include UK and overseas records, British UK 1881 census records, births, marriages and deaths and some parish records. Again this is a resource which is constantly expanding.
These on-line resource do need to be treated with some caution. Where records have been transcribed, you are relying on the accuracy of the person transcribing the records and their ability to read the original source. And of course a perennial problem with the Gunnee study is the variations / errors which have been transcribed eg. Gunnie, Gunnce, so it is important to use the searches to refer back to original records.