My personal favorites of those they list are the Conway Stewart 100 for a higher price pen, the Pilot Capless in the midrange, and the Kaweco Sport at the lower price range.  Each of those come in a variety of colors and materials that don’t impact performance. (I’m not familiar with Monaggio.)

The article includes a section on, “How to buy the best fountain pen for you”.

Best fountain pens 2018: Executive pens from just £18

…A joy to write with and a chance to leave your unique mark – buy the right fountain pen for you and writing notes and letters will no longer prove a chore. Check out our reviews below to find out more….

1. Monaggio Fountain Pen Set Fine to Medium Nib Original Bamboo Wood: Best fountain pen under £18

2. Pilot Capless Fountain Pen Birch Wood Barrel Red: The best for never losing the cap

3. The Writing Desk Conway Stewart 100 Cherry Red: The best luxury fountain pen

4. Cross ATX fountain pen in rose gold: The best for a modern look

5. Kaweco Sport Classic Chess Fountain Pen B: The best compact fountain pen

6. Waterman Expert Black Fountain Pen GT: The best pro-style fountain pen

http://www.expertreviews.co.uk/accessories/1407091/best-fountain-pens