I'll have to do it from system menu as putting in any game disc at any point brings up the error message and requires a reboot. I'll give it a go tonight and report back, many thanks.
Sorry for the quick answers but yes, yes and yesCould unplug the disc drive. As in, take the connector thing off the motherboard? Then boot it and see how it behaves? How do I get Priiloader again? Just use ModMii and tell it I'm on 4.3 now?

sysCheck v2.1.0b19 by Double_A and R2-D2199, Nano
...runs on IOS58 (rev 65535).
Region: PAL
System Menu 4.3E (v514)
Priiloader installed
Could not detect the drive date!
Homebrew Channel 1.1.2 running on IOS61
HomebrewFilter ist nicht installiert
Hollywood v0x11
Console ID: 120833729
Boot2 v4
Found 70 titles.
Found 50 IOS on this console. 5 of them are stub.
IOS3 (rev 65280): Stub
IOS4 (rev 65280): Stub
IOS9 (rev 65535): Trucha Bug
IOS10 (rev 768): Stub
IOS11 (rev 65535): Trucha Bug
IOS12 (rev 526): No Patches
IOS13 (rev 1032): No Patches
IOS14 (rev 1032): No Patches
IOS15 (rev 1032): No Patches
IOS16 (rev 512): Stub
IOS17 (rev 65535): Trucha Bug
IOS20 (rev 65535): Trucha Bug
IOS21 (rev 65535): Trucha Bug
IOS22 (rev 1294): No Patches
IOS28 (rev 65535): Trucha Bug
IOS30 (rev 65535): Trucha Bug
IOS31 (rev 3608): No Patches
IOS33 (rev 65535): Trucha Bug
IOS34 (rev 3608): No Patches
IOS35 (rev 65535): Trucha Bug, ES Identify, NAND Access
IOS36 (rev 65535): Trucha Bug, ES Identify, NAND Access
IOS37 (rev 65535): Trucha Bug, NAND Access
IOS38 (rev 65535): Trucha Bug
IOS40 (rev 65535): Trucha Bug
IOS41 (rev 65535): Trucha Bug
IOS43 (rev 65535): Trucha Bug
IOS45 (rev 65535): Trucha Bug
IOS46 (rev 65535): Trucha Bug
IOS48 (rev 65535): Trucha Bug
IOS50 (rev 65535): Trucha Bug
IOS51 (rev 4864): Stub
IOS52 (rev 65535): Trucha Bug
IOS53 (rev 65535): Trucha Bug
IOS55 (rev 65535): Trucha Bug
IOS56 (rev 65535): Trucha Bug
IOS57 (rev 65535): Trucha Bug
IOS58 (rev 65535): Trucha Bug, USB 2.0
IOS60 (rev 65535): Trucha Bug
IOS61 (rev 5662): No Patches
IOS62 (rev 6430): No Patches
IOS70 (rev 65535): Trucha Bug
IOS80 (rev 65535): Trucha Bug
IOS202[60] (rev 65535, Info: hermesrodries-v6): Trucha Bug, NAND Access, USB 2.0
IOS222[38] (rev 4, Info: hermes-v4): Trucha Bug, ES Identify, NAND Access, USB 2.0
IOS223[38+37] (rev 4, Info: hermes-v4): Trucha Bug, ES Identify, NAND Access, USB 2.0
IOS224[57] (rev 65535, Info: hermesrodries-v6): Trucha Bug, NAND Access, USB 2.0
IOS236 (rev 65535): Trucha Bug, ES Identify, NAND Access
IOS249[56] (rev 21008, Info: d2x-v8final): Trucha Bug, NAND Access, USB 2.0
IOS250[57] (rev 21008, Info: d2x-v8final): Trucha Bug, NAND Access, USB 2.0
IOS254 (rev 65281): BootMii
BC v6
MIOS v10
Report generated on 2015/03/08.