Serco are also housing many of the illegal immigrants who are coming across in inflatable boats. They have a £4 billion government contract and are putting the boat people up in 4 star hotels that many of the public, especially in these harsh economic times, can only dream of staying at. Serco seem to have their fingers in many dirty pies.
The UK apps (original VMWare Pivotal and new Google/Apple ENF app) were developed by NHSX, the digital development arm of the NHS in conjunction with various IT contractors. From https://www.wired.co.uk/article/nhs-covid-19-tracking-app-contact-tracing:
"The app has been developed by the NHS and NHSX, the innovation arm of the health service, under the direction of the DHSC. Software firms Zuhlke Engineering and Pivotal have been involved in the development though NHSX has not published a full list of companies who have worked on the app.
All the source code behind the app has been made open source and is available on GitHub. There’s also a privacy notice and data protection impact assessment on the government’s website. Both of these – at the time of writing are for the second app’s trials – detail how the app handles information and the methods used to create it. For the first version of the app, these documents were not published until the app had already been tested."
Serco do appear to have some software-development capacity, but I have found no evidence that they have been involved with NHSX, other than their role to provide staff for the manual contact tracing tasks based on interviewing infected people to determine their contacts. The manual process is potentially far more intrusive than the app - e.g. "where did you go on Tuesday last week?".
Note that the source code of the app is in the public domain (see link above), and the new app based on the Google/Apple Exposure Notification Framework (ENF) does not use a centralized data model, or record location data as part of the Bluetooth handshakes.
There's more info on the history of the first and second UK apps here:

NHS Covid-19 contact-tracing app to be launched in England and Wales
The contact-tracing app offers QR code check-in capability, allows users to book a free test and has an isolation countdown timer.

