When you say tactical vest, I'm assuming you mean it's something like this?
The Mayflower APC on the other hand is a plate carrier.
As far as I know they're one of the best brands for real steel / mil-spec kit but the quality is certainly reflected in the price. I haven't seen anything Mayflower sold in the UK before. If you wanted to import one it would cost a lot in tax and import duty etc.
If you're looking for good quality gear like the Mayflower that is made by those kind of companies (i.e. not replica airsoft stuff) Tactical Kit is my favourite site to look for it.
UK Tactical is also very good but doesn't have as much of a selection (as in there are less different companies rather than the number of products)
However, UK Tactical do exclusively stock Warrior Assault Systems gear (they have sales on all the time as well)
http://uktactical.com/c-54-warrior-assault-systems.aspx
It's a UK company with the stuff made in Vietnam IIRC.
Their DCS plate carrier is brilliant and everyone says how good they are. Similar to how everyone recommends the G&G Combat Machine when someone's looking for their first AEG.
Warrior pouches are really good quality too, as you'd expect. Of course, there are loads of other options for pouches as well though.
They have bungee / paracord retention with pull tabs rather than velcro flaps so they're faster, quieter and easier to use
http://uktactical.com/c-328-elite-ops-mag-pouches.aspx
Hope this helps and welcome to the forum by the way.