Please, no need to shout (which is what writing in CAPS means).

What is it you are confused about?

As to your price comparison, did you take the mandatory reservations for Eurostar (30€ in 2nd class) and in France (10 or 20€ per person and high speed train) into account?

Eurostar London St. P. Int. - Paris Nord (reservation 30€ per person) 

TGV Paris GDL - Perpignan (10 or 20€ reservation per person)

Same to get back. You can check the timetable on sncf-connect.com (bit confusing website) or other timetable websites like bahn.com or fahrplan.oebb.at

You can get reservations via Interrail.eu reservation service (+2€ fee/train/person), B-Europe (Eurostar and TGV within france) (+4€ fee/booking) or via SNCF Call Center (press #85 for English) or B-Europe (SNCB/NMBS International - Belgian Railways) but there will be phone charges instead

Hello I’ve lowered the case as didn’t realise that’s what it meant! 

Thanks for your replies

My initial confusion is what type of pass to get as I’m starting in London and this will affect with the additional bookings the overall cost. 

how many days pass would you recommend for below? 3 or 4 days?? 

london-paris 16.08

paris-perpignan 18.08

perpignan-paris-london 28.08

You'll need a global pass and the minimum is then 4 days.

If you take a 3-day pass for France, then Eurostar is not included and you'd need to buy separate tickets for Eurostar. If that's cheaper or not depends on the fares available.

You can check availability of pass holder reservations easily via B-Europe as mentioned by Angelo (Eurostar and TGV within france).