Cruciform keys are common in Portugal, and we had one on several visits to Spain.
Therefore, there is a common need for replacement keys. Which in turn means there is a common need for a cruciform key cutter.
On line, it appears to be more commonly referred to as a cross key, and technically as an E111 key cutter.
It retails for a little over €300.
Where is the nearest key cutter to the OC? Look a little further up the high street (Rua Direita) and there is an odds-and-ends shop that does key cutting now.
Did it do cruciform key cutting in 2007? I don't know, nor do I care. I have no doubt that 7-8 mins away in Lagos there would have been a cruciform key cutter in 2007, given that the key type is so common.
From what I can see re the cleaners' statements, they were given keys at the start of the day and handed them back at the end of the day. I could not find any requirement to hand them back if they went off-site during a lunch break.
Key control appears to have been a weak security point. MW staff would place cots in the apartments of MW clients who needed them, so they must have been given access to keys.
That makes the people with access to keys as - OC 24hr reception, cleaners, repair men, MW staff placing cots, staff doing check-ins on the MW bus from Faro to the OC.