Transfer at Undervalue and Preferences are no longer a Bankruptcy Offence but may be used as grounds for a Bankruptcy Restriction Order (BRO)

Technically yes, is the short answer but practically no. It largely depends on the amount. Your trustee will go through your finances with a fine tooth comb and if it is found you have significantly disadvantaged your creditors by disposing of an asset, that transaction can in theory be reversed. This would be expensive for all concerned.

You can't just give money to someone else when you are insolvent - especially if you intend to declare yourself bankrupt. This can lead to a bankruptcy restriction order which means the effects of bankruptcy will continue for at least 3 years.

There isn't enough information to comment on your specific situation. You should seek some specialist advice.

is there a time period specified during which they don't look further back for asset transfers, ie if the transfer was made 6 months before bankruptcy?

From your question I'm guessing that you are going to try to delay your bankruptcy and try to reverse the situation back to what it was before you made the transaction with your wife. This is a good idea if possible. You should at least make an effort to show your wife paying you back the money you loaned her.

There are specific time frames - which would cause a bankruptcy offence to have been committed if you have transferred a significant asset to a third party without getting anything in return - thereby making the creditors worse off - a "transaction at undervalue".

I can look them up - but the rule of thumb is that the Trustee can examine the last 6 years of your financial affairs. From memory, making a "transaction at undervalue" to an associated party within 2 years would be a bankruptcy offence.

I'm not saying that you won't get away with it, but I can't advise you to do it.