Hey David,
a .htaccess redirect is a possible solution, yet it is relatively inflexible since you’d have to modify the root file every time you add a new redirect. A simpler back-end solution would be to use the “link” project format, as I mentioned above; let me explain: in Ikebana, there are several possible formats any post or a project can have: “standard”, “image”, “video”, “quote”, “link”, etc. Each of them is pre-styled and optimized for a specific type of content, as follows from their names (you can read more about the post formats in WordPress on their official website here). You can set the format for the particular project from the “Format” settings box while in the editor mode for that project. Now, if a portfolio project has a “link” format, it becomes simply a link to another URL, which I suppose is exactly what you need; “link” format projects can also have thumbnails, so all you need to do is to change the format on existing projects from “standard” to “link” and instead of the content input the URL of the category (e.g. http://thedickers.co.uk/balimonster/category/family-2/carolyn/). You can read more about the post formats on pages 8-9 of the theme manual.
Regarding the dropdown menu issue you’ve mentioned: could you please clarify?
Sincerely,
Andrii / Satori Studio