Completely new to the volvo p1800 world, Can someone breakdown the differences between P1800, P1800S and P1800E? Engine size etc..

There are several books worth reading if you're interested in more history. The two I have are Bill Webb's "Swedish Iron AKA Volvo 1800" and "Volvo 1800 Gold Portfolio" published by Brooklands Books Ltd. I recently ordered another, "Volvo 1800: The Complete Story" by David Styles.

P1800 - The first few years of Jensen production, B18 engine @ 100 HP. Notalbe differences are 'cowhorn' bumpers, big finned hubcaps, and a script 'Volvo' on the B pillar.

1800S - The final assembly moved to the Swedish Lundby plant, when 120 series production moved to the new Torslanda plant. Flat bumpers, 122 style hubcaps and silver slotted wheels (or did that happen in '65?), B18 initially @ 108 HP, then up to 115 from '65 to '68. Gradual minor changes in trim, grille textures.

1800S - late 68 and '69 saw the fitting of the 118 HP B20 carb engine

1800E - '70 - '72 - the biggest upgrade. 130 HP B20E fuel injected engine, 4 wheel power disc brakes, flow through ventilation, more modern looking dash.

1800ES - '72 - '73 - short lives sport wagon version with small cargo area under a glass hatch instead of a trunk. With the B20F engine - detuned for smog to 112 HP.

Model P180:
P1800 - 1961-63 (roughly): the first 6000 cars assembled by Jensen in England. 1800cc, dual SU carbs, 100 HP.
1800S - 1964-68: Swedish production. 1800cc, dual SU carbs, 108 and later 115 HP.
1800S - 1969: The least-produced year. 2000cc, dual Stromberg carbs, 118 HP.

Model P182:
1800E - 1970-71: 2000cc, high compression, Bosch electronic fuel injection, 130 HP.
1800E - 1972: The last coupe. 2000cc, low compression, Bosch EFI, 112 HP.

Model P183:
1800ES - 1972-73: The "sportwagon." Same engine as the '72 coupe.

Some markets retained the 130 HP motor until the end, but not in North America.