I suppose the Chilterns merge into the south Cotswolds.
Not really: they are a fair distance apart, with quite a lot of Oxfordshire in between. You can stand on the escarpment of the Chilterns at Princes Risborough or Stokenchurch, where the roads particularly the M40 all fall over the edge of that escarpment, and look across towards the Cotswolds, but you won't actually see them. The Cotswolds are in Gloucestershire and West Oxfordshire, (and parts of Wiltshire, Somerset, Worcestershire and Warwickshire); the Chilterns are in East Oxfordshire, Buckinghamshire, Hertfordshire, and Bedfordshire.
Both ranges of hills slant roughly north-east to south-west on the map, so they are parallel rather than converging at any point.