got my engine management light on just read the error codes

P0030 1/1 02 Sens Heater Relay Malfunction
P0038 HO2S Heater Ctrl Circ Hi Bank1 Sens2
P0135 1/1 O2S Heater Failure
P0141 1/2 02 Sens Relay
P0138 1/2 O2S Shorted To Voltage
P0130 1/1 02 Sens Heater Relay Malfunction

am i right in thinking both the engine downpipe 02 and 02 sensor at the cat need replacing?

also my local motorfactors want £69.00 for each sensor. i take it there original bosch ones thats why so expensive. but you can get a none branded ebay ones for £20.00 each so do you think its best to get ones off ebay as its £50 saveing each and i need two.