Complex sentence: Part of ROF Thorpe Arch became the Boston Spa depository of the British Library; and a Hostel at ROF Swynnerton became a Training School for the General Post Office (GPO) Telephones, which later became British Telecom.
Split into simpler sentences: Part of ROF Thorpe Arch became the Boston Spa depository of the British Library. A Hostel at ROF Swynnerton became a Training School for the General Post Office (GPO) Telephones, which later became British Telecom.