The three months in Cyprus [at RAF Akrotiri] is a cost-effective way of giving the team a sustained period of training unbroken by lengthy poor weather conditions.
Whether or not a display aerobatic team needs to do a practice at the venue depends upon their NATO or National accreditation. If a foreign team [such as the French or Italians] have NATO accreditation, that is usually accepted by display organisers in the UK. For a team like the Swiss, [which are not part of NATO] then a display practice is usually called for, witnessed by a suitable flyer [eg Red Arrows Leader or Manager] before displaying in front of the public. I cannot tell you why Farnborough should be different.
Sometimes the team will do a practice anyway, especially if the venue is tricky to fly in [eg difficult terrain, etc].