Yes that still cause trouble as you stayed within the last 10days a high risk area You may can do this trip as there are no frequent controls but if they control you have to qurantine and pay it + a big penalty :/

I will stay in Amsterdam for about 24 hours, so is that still an issue then? and will be travelling from train 

Yes it´s still a problem as it counts where you stayed in the last days and not how you travel in fact i guess you won´t be controled on your Route but if they control (even within the Schengen Area they still sometimes control)

As Netherlands say non essential  visits from persons that stayed in the UK in the last days are forbidden :/

 

cool, I am travelling from London to Paris, Paris to Amsterdam and then Amsterdam to Brussels and finally returning to London,

any suggestion to change Amsterdam to? also do I get refund if I have seat reservation 

Reservation are usually exchangable but not refundable :)

Antwerp , Gent, Belgian Coast very beautifull and with a 70kilometers tramline connected, Strassbourg so many nice cities and villages in France and Belgium

thank you, you’ve been very helpful

how do I change seat reservation?

directly with the operating company is the bestway :)

I have changed my travel plan but I am still unclear on rules to Belgium 

So it’s now London to Paris

Paris to Geneva

and Geneva to Brussel 

then Brussel to London

Do you know if I can travel to Brussel without quarantine?

Check the Rules of Belgium on their own goverment websites As the rules change weekly :)