If you are looking for improving thinking, visualization, dreaming ability then take this combo few hours before going to sleep. Its actually not stimulant which affect sleep but helps in activating more brain regions associated with memory, thinking etc. Effects can be noticed both in sleep and during day time.
I read a long time ago that spreading out the intake of omega 3 over the day helps. I take 3x 330/180 epa dha over 24 hours.
These pills are considerably cheaper than £16/17 pm that you are paying, however, if it works for you that is what matters, and you probably get what you pay for.
Since you find omega 3 very useful definitely try Sharp PS Gold based supplement. Its clinically proven to improve memory. Various food supplement companies uses Sharp PS Gold based products. BrainBoost by Jarrow is one among them with added brain boosting ingredients.
Research article on effectiveness of Sharp PS Gold.
Make sure to take omega 3 close to bed time as it can affect rem sleep to give brain boosting effects just like liones mane mushroom. It can give vivid dreams due to better brain activation. Take it with dinner and give a gap of 3 hrs between dinner and sleep.