Obviousness and obfuscation
It should be obvious that proving something to the civil standard does not undermine failure to prove it to the criminal standard.
Blindingly obvious though this may be, it has troubled the Strasbourg judges. The UKSC was briefly troubled by it (R v Briggs-Price, noted here 2 May 2009), but more recently it was not: Gale v Serious Organised Crime Agency  UKSC 49 (26 October 2011).
Again in Gale the context was civil proceedings for the recovery of property to a value equivalent to the proceeds of serious criminal offending. The judge had applied the civil standard of proof to the issue of the commission of such offences. The Supreme Court unanimously upheld that approach.
There was some delicate treatment of Briggs-Price, and what was the minority view there was now unanimously approved: 47-54. This was achieved by admirably obscure reasoning, perhaps inspired the confusing nature of the Strasbourg jurisprudence.
The presumption of innocence, and the finality of acquittals, are not compromised where in civil proceedings for the recovery of the proceeds of crime the court is satisfied on the balance of probabilities that criminal offending had occurred.
Waiver of the right to legal advice
Another thing that you would have thought was obvious is that a person can waive the right to legal advice without having to receive legal advice about waiver and its consequences.
This point had to be decided in McGowan (Procurator Fiscal, Edinburgh) v B (Scotland)  UKSC 54 (23 November 2011).
Difficulties concerning the effectiveness of waiver can arise from the different rights that may be waived and from whether the alleged waiver was express or implied. But in all cases, waiver must be shown to have been "voluntary, informed and unequivocal" (Lord Hope at 17). "Informed" waiver will not exist if there is reason to believe the defendant had not understood the right that was being waived (36, 38, 44), but a defendant can understand without legal advice (46). The court will, however, proceed cautiously where the defendant is of low intelligence or is vulnerable for other reasons (47).
Further (49), if a defendant declines legal advice, the police should mention that such advice can be obtained by telephone, and if the defendant still declines, the police should ask why and record the answer. That, at least, would be best practice although not an absolute rule (50) [and see also Jude v HM Advocate (Scotland)  UKSC 46 (23 November 2011)]. It could also be wise to advise the defendant that legal advice could be given without cost to him (51).
There was a time when courts took a more tight-sphinctered approach to what was adequate advice of the right to consult a lawyer. In R v Piper  3 NZLR 540 (CA) for example, it was thought to be unnecessary to inform the defendant that the consultation would occur without the police overhearing it. But now we have the Chief Justice's practice direction (issued under s 30 of the Evidence Act 2006) which requires privacy to be mentioned. It also requires mention of the availability of free advice.
Another point I should make about waiver is this. Waiver is a more sensible requirement to use than is consent. The issue should not be whether the defendant "consented" to police questioning, but rather whether he waived his right to legal advice and to silence. Similarly, in the context of searches, the issue should not be whether the defendant "consented" to a search, but whether he waived his right not to be searched. As anyone can see, it is incongruous to think that a defendant in possession of incriminating material would freely consent to being searched by the police, but less so to think that he might waive his right not to be searched.