JJ Pitchley bagged a hat-trick in the Raiders’ 4-2 home success and Marek Nahlik matched the feat in their 7-1 win in the return game.
League and cup winners Chelmsford Chieftains remain on course for the treble after completing a 10-4 overall success over Bracknell Hornets.
Juraj Huska (2) topped the scoring in the Chieftains’ 4-2 road victory, while Brandon Ayliffe hit a hat-trick in the 6-2 success on home ice.
Invicta Dynamos are also through to the last four after sealing a 9-6 aggregate success against MK Thunder.
The Dynamos won 3-1 on home ice and followed up with a 6-5 win in the reverse fixture.
Streatham IHC booked their semi-final place after a 5-4 overall victory over Solent Devils.
The teams were tied at 2-2 after the first leg, but Streatham squeezed through after picking up a 3-2 home win.
Cardiff Fire completed their regular season fixtures in D2S with a 10-2 victory at Swindon Wildcats NIHL.
Peterborough Islanders, Chelmsford Warriors and Bristol Pitbulls all recorded home wins, while Ross Sin-Hidge’s hat-trick helped Lee Valley Lions to a 6-4 win at Haringey Racers.
NIHL1 South play-offs
Bracknell Hornets 2-4 Chelmsford Chieftains
Chelmsford Chieftains 6-2 Bracknell Hornets (agg 10-4)
Invicta Dynamos 3-1 MK Thunder
MK Thunder 5-6 Invicta Dynamos (agg 6-9)
London Raiders 4-2 Oxford City Stars
Oxford City Stars 1-7 London Raiders (agg 3-11)
Solent Devils 2-2 Streatham IHC
Streatham IHC 3-2 Solent Devils (agg 5-4)
Bristol Pitbulls 7-4 Basingstoke Buffalo
Chelmsford Warriors 5-0 Slough Jets
Haringey Racers 4-6 Lee Valley Lions
Peterborough Islanders 11-4 Invicta Mustangs
Swindon Wildcats NIHL 2-10 Cardiff Fire
(Image permission: John Scott)