Nope.
Enthuisasts have "earmarked" the 315s for South Wales
"Pacers" refers solely to class 140-144, which are based on bus bodies mated to a modified, powered,
four wheel freight wagon chassis. They have 15m long coaches
The 315s are much much older design, being part of the "1972 design"; BR's first "modern" EMU design, often reffered to as the "PEP" design. This family also includes 313 (dual voltage 3 carriage, currently used by FCC, Southern (with pantograph stripped off) and Network Rail), 314 ( AC only, 3 carriage, ScotRail in the SPT area) and Merseyrails 507 and 508 fleet. They all share a 20-m carriage design. There's also some carriages of this design used in SWT's Class 455/8 subclass; this is because the 508s were originally 4-carriage and they were reused when the class was reduced to 3-car for use on Merseyrail. The 315s are 4-car, AC-only.